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Phytocompounds isolated from plants are well appraised for their broad pharmacological propensities in several pathologies. One key benefit of phytoconstituents is their relatively low toxicity and adverse effects. Nonetheless, poor solubility, permeation, and poor specificity at the target site tend to hinder its therapeutic efficacy. Hence, novel technologies for drug delivery systems are being developed via the use of various nanoformulation strategies to overcome these challenges and give uniform medication focusing at the dynamic site in desired concentration and improved therapeutic efficacy. Such approaches comprise of novel drug delivery systems (NDDS). The utilisation of herbal formulations for NDDS is more beneficial and advantageous as opposed to others. The utilisation of ethosome, liposome, emulsion, phytosomes, microsphere, and strong lipid nanoparticles of herbal formulation has improved the remedial impacts of plant extricates. With the utilisation of all these, directed delivery of the formulation is accomplished, because of which the formulation exhibits impact on the site, and its’ bioavailability is, likewise, expanded. With these novel medication conveyance frameworks, the actives and concentrates, which are utilised as part of natural formulations, exhibit a sustained release, enhancement in stability, improved therapeutic efficacy, and protection from toxicity. The primary motivation behind creating alternative drug delivery technologies is to expand the effectiveness of drug conveyance and safety in the process and give more comfort to the patient. In this review, the importance of various phytocompounds in the delivery of drugs is highlighted as well as their importance in reducing the risk or diseases.

Alzheimer’s disease (AD) and Parkinson's disease (PD) are notorious neurodegenerative diseases amongst the general population. Being age-associated diseases, the prevalence of AD and PD is forecasted to rapidly escalate with the progressive aging population of the world. These diseases are complex and multifactorial. Among different events, amyloid β peptide (Aβ) induced toxicity is a well‐established pathway of neuronal cell death, which plays a vital function in AD. Glutamate, the major excitatory transmitter, acts as a neurotoxin when present in excess at the synapses; this latter mechanism is termed excitotoxicity. It is hypothesised that glutamate-induced excitotoxicity contributes to the pathogenesis of AD and PD. No cure for AD and PD is currently available and the currently approved drugs available to treat these diseases have limited effectiveness and pose adverse effects. Indeed, plants have been a major source for the discovery of novel pharmacologically active compounds for distinct pathological conditions. Diverse plant species employed for brain-related disorders in traditional medicine are being explored to determine the scientific rationale behind their uses. Herein, we present a comprehensive review of plants and their constituents that have shown promise in reversing the (i) amyloid-β -related toxicity in AD models and (ii) glutamate-induced excitotoxicity in AD and PD models. This review summarizes information regarding the phytochemistry, biological and cellular activities, and clinical trials of several plant species in view to provide adequate scientific baseline information that could be used in the drug development process, thereby providing effective leads for AD and PD.

Background: Diabetes Mellitus (DM) is a severe endocrine metabolic disease coupled with various long-term complications. A plethora of targets have been identified, however, with possible adverse effects. Therefore, researchers are in the perpetual quest for safe and more effective therapeutics. Natural products, particularly derived from plants, have proven to exert anti-diabetic effects via diverse mechanisms. Methods: An overview of DM pathogenesis and its associated micro- and macro-vascular complications is presented. Possible underlying mechanisms of herbal remedies in DM management are provided, highlighting some key therapeutic targets. The review also appraises the recent progress of herbal products in treating DM through regulating inflammation and gut microbiota. Finally, currently available pharmacological treatments are discussed. Results: The results show that numerous plants have proven to be promising sources of insulin secreting agents, α-glucosidase and α-amylase inhibitors. Among the non- conventional targets, inhibition of key enzymes such as lipase, cholinesterases and angiotensin converting enzyme has been directly and/or indirectly linked to DM and DM complications. For instance, hypericin, pseudohypericin and I3,II8-biapigenin isolated from Hypericum perforatum L., and palmatine and columbamine isolated from Dichocarpum auriculatum (Franch.) W. T. Wang & P. K have been found to be powerful lipase and cholinesterase inhibitors, respectively. Moreover, a number of plant-derived compounds such as feruloylated oligosaccharides from maize bran, baicalein and berberine are reported to mediate anti-diabetic property via modulation of gut microbiota. Conclusion: The information amassed in this review is anticipated to provide useful scientific baseline information to support advanced research in natural antidiabetic drug development.

Pathogenic microorganisms should be considered as the number one foe of human, as witnessed by recent outbreaks of coronavirus disease (COVID-19) and with bacteria no longer sensitive to existing antibiotics. The resistance of pathogenic bacteria and deaths attributable to bacterial infections is increasing exponentially. Bacteria used different mechanisms to counterattack to existing antibiotics, namely (i) enzymatic inhibition, (ii) penicillin-binding protein modification, (iii) porin mutations, (iv) efflux pumps and (v) molecular modifications of antibiotic targets. Developing new antibiotics would be time-consuming to address such a situation, thus one of the promising approaches is by potentiating existing antibiotics. Plants used synergism to naturally defend and protect themselves from microbes. Using the same strategy, several studies have shown that the combinations of natural products and antibiotics could effectively prolong the lifespan of existing antibiotics and minimize the impact and emergence of antibiotic resistance. Combining essential oils constituents, namely uvaol, ferruginol, farnesol and carvacrol, with antibiotics, have proved to be efficient efflux pump inhibitors. Plant-derived compounds such as gallic acid and tannic acid are effective potentiators of various antibiotics, including novobiocin, chlorobiocin, coumermycin, fusidic acid, and rifampicin, resulting in a 4-fold increase in the potencies of these antibiotics. Several lines of research, as discussed in this review, have demonstrated the effectiveness of natural products in potentiating existing antibiotics. For this reason, the search for more efficient combinations should be an ongoing process with the aim to extend the life of the ones that we have and may preserve the life for the ones that are yet to come.

The recent emergence of Zika virus (ZIKV) in Brazil and the increasing resistance developed by pathogenic bacteria to nearly all existing antibiotics should be taken as a wakeup call for the international authority as this represents a risk for global public health. The lack of antiviral drugs and effective antibiotics on the market triggers the need to search for safe therapeutics from medicinal plants to fight viral and microbial infections. In the present study, we investigated whether a mangrove plant, Bruguiera gymnorhiza (L.) Lam. (B. gymnorhiza) collected in Mauritius, possesses antimicrobial and antibiotic potentiating abilities and exerts anti-ZIKV activity at non-cytotoxic doses. Microorganisms Escherichia coli ATCC 25922, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 70603, methicillin-resistant Staphylococcus aureus ATCC 43300 (MRSA), Salmonella enteritidis ATCC 13076, Sarcina lutea ATCC 9341, Proteus mirabilis ATCC 25933, Bacillus cereus ATCC 11778 and Candida albicans ATCC 26555 were used to evaluate the antimicrobial properties. Ciprofloxacin, chloramphenicol and streptomycin antibiotics were used for assessing antibiotic potentiating activity. ZIKVMC-MR766NIID (ZIKVGFP) was used for assessing anti-ZIKV activity. In silico docking (Autodock 4) and ADME (SwissADME) analyses were performed on collected data. Antimicrobial results revealed that Bruguiera twig ethyl acetate (BTE) was the most potent extract inhibiting the growth of all nine microbes tested, with minimum inhibitory concentrations ranging from 0.19–0.39 mg/mL. BTE showed partial synergy effects against MRSA and Pseudomonas aeruginosa when applied in combination with streptomycin and ciprofloxacin, respectively. By using a recombinant ZIKV-expressing reporter GFP protein, we identified both Bruguiera root aqueous and Bruguiera fruit aqueous extracts as potent inhibitors of ZIKV infection in human epithelial A549 cells. The mechanisms by which such extracts prevented ZIKV infection are linked to the inability of the virus to bind to the host cell surface. In silico docking showed that ZIKV E protein, which is involved in cell receptor binding, could be a target for cryptochlorogenic acid, a chemical compound identified in B. gymnorhiza. From ADME results, cryptochlorogenic acid is predicted to be not orally bioavailable because it is too polar. Scientific data collected in this present work can open a new avenue for the development of potential inhibitors from B. gymnorhiza to fight ZIKV and microbial infections in the future.

Syringodium isoetifolium (Asch.) Dandy (Family: Cymodoceaceae) is a seagrass growing in the oceans across the globe except in cold waters. This study investigated into the polyphenolic content, antioxidant [2,2-diphenyl-1-picrylhydrazyl(DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid (ABTS), cupric reducing antioxidant capacity (CUPRAC), ferric reducing antioxidant power (FRAP), metal chelating, phosphomolybdenum)]and enzymatic properties [α-amylase, α-glucosidase, tyrosinase, acetylcholinesterase (AChE), butylcholinesterase (BChE)] of S. isoetifolium. Detailed phytochemical profiling was also conducted using Ultra Performance High-Pressure Liquid Chromatography (UHPLC) technique. The methanolic extract was found to possess greater amount of phenolic than flavonoid compounds. Antioxidant results showed that the extract was a better ABTS radical scavenger (9.56 ± 0.40 mg TE/g) compared to DPPH (5.39 ± 0.09 mg TE/g and exhibited good reducing potential with CUPRAC assay (18.66 ± 0.46 mg TE/g). In terms of enzymatic inhibition, strong activities were noted against tyrosinase (25.92 ± 0.11 mg KAE/g) in contrast to α-amylase, α-glucosidase and cholinesterase. Phytochemical data revealed the presence of 14 compounds with chicoric acid and caftaric acid among them. Docking the identified compounds, namely, caftaric acid, loliolide and Iso-loliolide at the active site of the tyrosinase enzyme has elucidated the binding affinity of these inhibitors and their interactions with the active site. Based on our findings, S. isoetifolium may be considered as a good natural antioxidant and clinical enzyme inhibitors that can be exploited in pharmaceutical/or cosmeceutical industries.

This study focused on the biological evaluation and chemical characterization of Geranium pyrenaicum Burm. f. Different solvent extracts (hexane, ethyl acetate, methanol, and water extracts) were prepared. The phytochemical profile, antioxidant, and enzyme inhibitory activity were investigated. Cytotoxicity was assessed using VERO, FaDu, HeLa and RKO cells. The antiviral activity was carried out against HSV-1 (Herpes simplex virus 1) propagated in VERO cell line. The aqueous extract, possessing high phenolic content (170.50 mg gallic acid equivalent/g extract), showed the highest reducing capacity (613.27 and 364.10 mg Trolox equivalent/g extract, for cupric reducing antioxidant capacity and ferric reducing antioxidant power, respectively), radical scavenging potential (469.82 mg Trolox equivalent/g extract, against 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)), metal chelating ability (52.39 mg ethylenediaminetetraacetic acid equivalent/g extract) and total antioxidant capacity (3.15 mmol Trolox equivalent/g extract). Liquid chromatography-electrospray ionization-quadrupole time-of-flight-mass spectrometry (LC-ESI-QTOF-MS/MS) alloved to tentatively identify a total of 56 compounds in the extracts, including ellagitannins, gallic acid and galloyl derivatives amongst others. The ethyl acetate extracts substantially depressed cholinesterase enzymes (4.49 and 12.26 mg galantamine equivalent/g extract against AChE and BChE, respectively) and α-amylase enzyme (1.04 mmol acarbose equivalent/g extract). On the other hand, the methanolic extract inhibited tyrosinase (121.42 mg kojic acid equivalent/g extract) and α-glucosidase (2.39 mmol acarbose equivalent/g extract) activities. The highest selectivity towards all cancer cell lines (SI 4.5–10.8) was observed with aqueous extract with the FaDu cells being the most sensitive (CC50 40.22 µg/mL). It can be concluded that the presence of certain bioactive antiviral molecules may be related to the high anti HSV-1 activity of the methanolic extract. This work has generated vital scientific data on this medicinal plant, which is a prospective candidate for the creation of innovative phyto-pharmaceuticals.

Members from the Verbascum genus are well appraised for their traditional uses against a variety of ailments including anti-inflammatory related disorders. This study thus attempts at validating the biological properties of two underexplored Verbascum members namely Verbascum euphraticum Benth. (V. euphraticum) and Verbascum oocarpum Murb. (V. oocarpum) in terms of their antioxidant and enzymatic inhibitory activities. Concentration of specific bioactive compounds was also established and molecular dynamic analysis were conducted on amassed data. Results showed that total phenolic and total flavonoid contents were higher for the methanolic extract of V. oocarpum compared to the methanolic extract of V. euphraticum. Phytochemical quantification revealed that the extraction solvents influenced the phytochemical composition of the extracts. Derivatives of phenolic acids such as 3-caffeoylquinic acid and 3,5-dicaffeoylquinic acid together with some phenolic acids i.e., gallic, vanillic, caffeic, syringic, p-coumaric and ferulic acid, have been detected in the extracts of both Verbascum species. Methanolic extracts of V. euphraticum and V. oocarpum yielded the highest total content of monitored compounds resulting in 162.758 and 3716.861 μg/g of dried weight extract, respectively. The methanolic extracts of both plants showed highest antioxidant potential while the ethyl acetate and hexane extracts were potent inhibitors of cholinesterase, α-amylase and α-glucosidase. Molecular dynamic results indicated that vanillic acid is able to make strong interactions with copper ions of tyrosinase, resulting into an effective anti-tyrosinase activity. In light of the above, both Verbascum species could be considered for future phytopharmaceutical development.

Cajanus cajan. (L.) Millsp. (C. cajan) (Family: Fabaceae) also known as pigeon pea, is a famous food and cover/forage crop bearing a high amount of key amino acids (methionine, lysine and tryptophan). This study investigated into the total phenolic (TPC), flavonoid content (TFC), antioxidant ]2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2 -azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), cupric reducing antioxidant capacity, total antioxidant capacity (TAC) (phosphomolybdenum) and metal chelating] activities and enzyme [alpha-amylase, alpha-glucosidase, tyrosinase, acetyl-(AChE), butyry1-(BChE) cholinesterase] inhibitory effects of four extracts (methanol, hexane, ethyl acetate, aqueous) prepared from C. cajan stem bark. Direct identification of antioxidants was also conducted using the high performance liquid chromatography-ferric reducing antioxidant power (HPLC-FRAP) system. The highest TPC and TFC were recorded with the methanolic (23.22 +/- 0.17 mg GAE/g) and ethyl acetate extracts (19.43 +/- 0.24 mg RE/g), respectively. The methanolic extract exhibited important antioxidant activity with DPPH (38.41 +/- 0.05 mg Trolox equivalent (TE)/g), ABTS (70.49 +/- 3.62 mg TE/g), CUPRAC (81.86 +/- 2.40 mg TE/g), FRAP (42.96 +/- 0.59 mg TE/g) and metal chelating (17.00 +/- 1.26 mg ethylenediaminetetraacetic acid equivalent/g). p-coumaric and caffeic acid were the predominant antioxidants in the samples. Results from enzymatic assays showed the potential abilities of hexane extract in inhibiting the AChE, BChE, alpha-amylase and alpha-glucosidase enzymes. From the results obtained in this study, it can be concluded that C. cajan can be considered as a promising source of antioxidants and key enzyme inhibitors that can be exploited for future bioproduct development.

Olive and olive oil (OO) are a fundamental component of the Mediterranean culture and cuisine. Diverse traditional medicines include olive and its oil as a vital ingredient for the formulation of concoctions useful against urinary tract infection, diabetes, high blood pressure, hair loss, diarrhea, gout, rheumatism, mouth, and as a skin cleanser in various parts of the world. The use of OO as a healthy culinary ingredient has remained in vogue compared to other cooking oils given its promising benefits on the cardiovascular system among other health benefits. Indeed, results derived from in vitro, in vivo, and clinical studies have validated the potential benefits of olive and OO for the cardiovascular system. In vitro, both the methanolic and the ethanolic leaf extract downregulate hydroxynonenal-induced p-MAPKAPK-2 and p-c-Jun. Olive and OO are rich in bioactive metabolites such as oleuropein (OLE), hydroxytyrosol, and polyphenols. Notably, OLE inhibits the excess production of reactive oxygen species and stabilized mitochondrial membrane potential following simulated ischemia-/reperfusion-induced cardiomyocyte injury. In vivo, OLE reduced the plasma lipid peroxidation products and protein carbonyl levels in rabbits alongside providing strong antioxidant protection. Interestingly, it can also reduce doxorubicin-related cardiotoxicity. Both hydroxytyrosol and OLE significantly reversed chronic inflammation and oxidative stress consequently reducing cardiovascular, hepatic, and metabolic symptoms. Polyphenols also reduce chronic inflammation and oxidative stress. In furtherance, extra-virgin oil has demonstrated both cholesterol and blood pressure lowering properties while clinically decreasing cardiovascular disease risk by at least 35%. Virgin OO provides benefits among patients with stable coronary heart disease and can be employed as a supplement in patients with this disease.

Mitracarpus hirtus (L.) DC. (Family: Rubiaceae) is a tropical annual herb commonly found in America and Mexico. In the present study, the methanol, ethyl acetate, dichloromethane and aqueous extracts of the plant were tested for total phenolic (TPC) and flavonoid content (TFC) and antioxidant activities were evaluated using a battery of assays including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), ferric reducing antioxidant power (FRAP), cupric reducing antioxidant capacity, total antioxidant capacity (TAC) (phosphomolybdenum) and metal chelating. Enzyme inhibitory effects were investigated using acetylcholinesterase (AChE), tyrosinase, α-amylase and α-glucosidase as target enzymes. The phytochemical profile was obtained using liquid chromatography-diode array detection-electrospray ionization-mass spectrometry (LC-DAD-ESI-MSn), liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MSn) and nuclear magnetic resonance (NMR) experiments. Results showed that the dichloromethane and ethyl acetate extracts yielded the highest TPC (29.10 ± 0.07 mg gallic acid equivalent/g) and TFC (38.14 ± 0.91 mg rutin equivalent/g), respectively. Aqueous extract showed weak activity against tested enzymes but demonstrated the strongest ABTS scavenging activity (59.39 ± 1.19 mg trolox equivalent/g) and is the strongest Fe3+ reducer (59.42 ± 0.59 mg trolox equivalent/g). Phytochemical analysis revealed the presence of phenolics, pyrrolizidine alkaloids and triterpene acid. This is the first report gathering scientific data on antioxidant, enzyme inhibitory activities and phytochemical composition of M. hirtus and the obtained results can be used as starting point for further investigation on this traditional medicinal herb.

This research study presents information for the first time on the nutritionally relevant lipophilic compounds obtained from Ecklonia radiata, a poorly studied brown kelp. The major lipophilic compounds were analyzed utilizing liquid chromatography (LC)-tandem mass spectrometry (MS/MS) and gas chromatography (GC)-mass spectrometry (MS). The LC-MS/MS results revealed the presence of eight major lipophilic compounds, including sterols, carotenoids, vitamin E, and phylloquinone (vitamin K1). Quantitative analysis showed that fucosterol was the most predominant phytosterol in the fronds and stipes of E. radiata. The carotenoids (all-E)-fucoxanthin and (all-E)-β-carotene were present in higher yield. In terms of vitamin E, α-tocopherol was identified as the main tocol. The coenzyme, phylloquinone, important for protein synthesis, was also identified in E. radiata. GC-MS identified 13 fatty acids with palmitic (C16:0) and oleic acid (C18:1n9c) present in the highest quantities. To our knowledge, this is the first report on E. radiata, and the valuable data presented herein can be used as a baseline for developing novel nutraceuticals.

Bruguiera gymnorhiza (L.) Lam. is claimed to effectively manage a number of ailments including diabetes and associated complications. Nonetheless, no attempt has been made to delineate its pharmacological propensities and phytochemical profile. This study was designed to appraise the antioxidant and enzymatic inhibitory properties relevant to the management of diabetes mellitus, obesity, and neurodegenerative and skin disorders. A combination of colorimetric assays and ultra-high-performance liquid chromatography/electrospray ionization tandem mass spectrometry (UHPLC-ESI-MS/MS) were applied for the phytochemical screening of leaf, root, twig, and fruit extracts (methanol and ethyl acetate). In vitro antioxidant evaluations were via radical scavenging abilities (DPPH, ABTS), reducing potential (FRAP, CUPRAC), chelating power, and total antioxidant capacity (phosphomolybdenum). Seven key metabolic enzymes (&alpha, amylase, &alpha, glucosidase, tyrosinase, elastase, lipase, AChE, and BChE) were targeted to determine the inhibitory effects. Multivariate and in silico docking analysis were performed on collected data. Methanolic fruit extract yielded the highest total phenolic, tannin, and triterpenoid contents (174.18 &plusmn, 4.27 mg GAE/g, 176.24 &plusmn, 3.10 mg CE/g, 63.11 &plusmn, 3.27 mg OAE/g, respectively), significantly depressed tyrosinase, elastase, and &alpha, amylase activities (155.35 &plusmn, 0.29 mg KAE/g, 4.56 &plusmn, 0.10 mg CAE/g, 1.00 &plusmn, 0.05 mmol ACAE/g, accordingly), and harboured the most potent antioxidant capacities with DPPH, CUPRAC, FRAP (492.62 &plusmn, 5.31, 961.46 &plusmn, 11.18, 552.49 &plusmn, 8.71 mg TE/g, respectively), and phosphomolybdenum (4.17 &plusmn, 0.31 mmol TE/g) assays. Multivariate analysis suggested that the type of solvents used influenced the biological activities more compared to plant parts. Docking analysis showed that azelaic acid binds with tyrosinase by Van der Waals and conventional hydrogen bonds. We anticipate that the present study may establish baseline data on this halophyte that could open new avenues for the development of biomedicine.

Seaweeds have been exploited as both food products and therapeutics to manage human ailments for centuries. This study investigated the metabolite profile of five seaweeds (Halimeda spp., Spyridia hypnoides (Bory de Saint-Vincent) Papenfuss, Valoniopsis pachynema (G. Martens) B&oslash, rgesen, Gracilaria fergusonii J. Agardh and Amphiroa anceps (Lamarck) Decaisne using ultra-high-performance liquid chromatography coupled with electrospray ionization mass spectrometry (UHPLC-ESI-MS/MS). Furthermore, these seaweeds were assessed for antioxidant and inhibitory effects against &alpha, amylase, &alpha, glucosidase, acetyl-cholinesterase (AChE), butyryl-cholinesterase (BChE) and tyrosinase. Valoniopsis pachynema and A. anceps yielded the highest flavonoid (4.30 &plusmn, 0.29 mg RE/g) and phenolic content (7.83 &plusmn, 0.08 mg RE/g), respectively. Additionally, A. anceps exhibited significant antioxidant properties with all assays and significantly depressed BChE (IC50 = 6.68 &plusmn, 0.83 mg/mL) and &alpha, amylase activities (IC50 = 5.34 &plusmn, 0.14 mg/mL). Interestingly, the five seaweeds revealed potent inhibitory effects against tyrosinase activity. In conclusion, A. anceps might be considered as a key source of phytoantioxidants and a potential candidate to develop nutritional supplements. Besides, the five tested seaweeds warrant further study and may be exploited as promising natural sources for managing hyperpigmentation.

Vitellaria paradoxa C. F. Gaertn. (Family: Sapotaceae), is a well-known medicinal plant but with no consolidated published literature to substantiate its traditional uses. This research aimed to investigate the pharmaceutical potential of V. paradoxa extracts and attempts to compare the biological profiles and phytochemical analysis prepared by different extraction protocols. For preparation of the V. paradoxa leaves and stem bark extracts, four extraction techniques and two different solvent types were employed. First analysis included identification of bioactive compounds by use of high-resolution Quadrupole Time-Of-Flight instrument. Antioxidant capacities were evaluated as radical scavenging potential, reducing potential, total antioxidant capacity (phosphomolybdenum) and metal chelating power. The last evaluation step included analysis of the inhibitory properties of V. paradoxa extracts against key enzymes related to main health problems. Our findings revealed key details on phytochemical profiling of the V. paradoxa plant, whereas 17 phytochemicals were identified in leaves and 14 in stem bark. Antioxidant assays showed that extracts obtained by maceration extraction process exhibit potent antioxidant capacities. Extracts prepared by HAE generally showed the highest enzymatic activities. The presented findings confirmed the need for further studies geared towards discovery and development of novel bioactive components from V. paradoxa leaves and stem bark.

Africa is famous for its floral biodiversity, exploited by local people for therapeutic purposes. However, such plants need to be scrutinised scientifically for the presence of bioactive compounds and possible biological properties. This study attempts for the first time to highlight the pharmacological and phytochemical profile of extracts prepared from leaves and stem barks of three African plants (Macaranga hurifolia Beille, Sterculia tragacantha Lindl. and Zanthoxylum gilletii (De Wild.) P. G. Waterman. The extracts were tested for antioxidant and enzyme inhibitory effects. Free radical scavenging, metal chelator, reducing power and phosphomolybdenum assays were performed to evaluate antioxidant effects. To identify enzyme inhibitory effects, cholinesterases (acetylcholinesterase (AChE) and butrylcholinesterase (BChE)), tyrosinase, α-amylase and α-glucosidase were selected as target enzymes. High performance liquid chromatography-Electrospray tandem mass spectrometry (HPLC-ESI-MS) technique was also used for chemical profiling. ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) and DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging assays showed that the stem barks of all three African plants were better scavenger than leaf extracts. Sterculia tragacantha was found to be a better metal chelator (64.10 ± 4.66 mg EDTAE/g) among the studied plants. All extracts exhibited good clinical enzyme inhibitory activities. The stem bark of S. tragacantha exhibited the best acetylcholinesterase activity compared to the other plants. HPLC-ESI-MS characterization showed that the most abundant compounds in stem bark were flavonoids in M. hurifolia (4.2 ± 0.2 mg/g DE), proanthocyanidins in S. tragacantha (42 ± 1 mg/g DE) and similar concentrations of phenolic acids and flavonoids in Z. gilletii (2.8–3.1 mg/g DE). Based on the biological activity, the most abundant and relevant bioactive compounds in the extracts were studied using molecular modelling approach against tyrosinase. The studied African plants showed good antioxidant and enzymatic propensities and thus can be considered as potential bioresources for future development of nutraceuticals and/or for pharmaceutical applications.

Currently, there is a growing interest in screening and quantifying antioxidants from biological samples in the quest for natural and effective antioxidants to combat free radical-related pathological complications. Antioxidant assays play a crucial role in high-throughput and cost-effective assessment of antioxidant capacities of natural products such as medicinal plants and food samples. However, several investigators have expressed concerns about the reliability of existing in vitro assays. Such concerns arise mainly from the poor correlation between in vitro and in vivo results. In addition, in vitro assays have the problem of reproducibility. To date, antioxidant capacities are measured using a panel of assays whereby each assay has its own advantages and limitations. This unparalleled review hotly disputes on in vitro antioxidant assays and elaborates on the chemistry behind each assay with the aim to point out respective principles/concepts. The following critical questions are also addressed: (1) What make antioxidant assays coloured? (2) What is the reason for working at a particular wavelength? (3) What are the advantages and limitations of each assay? and (4) Why is a particular colour observed in antioxidant–oxidant chemical reactions? Furthermore, this review details the chemical mechanism of reactions that occur in each assay together with a colour ribbon to illustrate changes in colour. The review ends with a critical conclusion on existing assays and suggests constructive improvements on how to develop an adequate and universal antioxidant assay.