Search

The efficacy of an organogenesis based regeneration protocol and the occurrence of somaclonal variation has been studied up-to eighth subculture of Hibiscus sabdariffa L. var. HS4288. Initially, the induction of organogenic calli from 83.33% root explants was standardized in 2.26 μM 2, 4-Dichlorophenoxyacetic acid (2, 4-D) and 4.65 μM kinetin (KIN) supplemented Driver-Kuniyuki Walnut (DKW) basal medium. The calli were maintained up to the eighth subculture (each with 6-weeks duration) in the same basal medium along with 1.13 μM 2, 4-D and 4.65 μM KIN. The highest regenerative efficiency of the root-derived calli was found in 1.08 μM α-Naphthaleneacetic acid (NAA) and 8.88 μM 6-Bezyladenine (BA) containing DKW medium. This particular medium produced 14.30 ± 0.47 numbers of visible shoots (>10 mm in length) at the first subculture from 425 ± 35 mg of callus through the process of organogenesis. The morpho-histological study confirmed the organogenic mode of regeneration. With the gradual increase of culture passage, the frequency of shoots was steadily declined. The genetic polymorphism of the regenerated plants from eight successive sub-cultures was assessed using three different single primer amplification reaction (SPAR) methods; viz. Random amplified polymorphic DNA (RAPD), Direct amplification of minisatellite DNA (DAMD) and Inter simple sequence repeat (ISSR) markers. The SPAR analysis revealed that up to fifth subculture all the three types of primers produced the monomorphic banding pattern among the regenerated plants with that of their mother plant. From the sixth subculture onwards there were some alterations in banding profiles both in RAPD and ISSR markers but DAMD marker did not show any polymorphism up to eighth subculture. In the present work, the highest polymorphism percentage was recorded among the plants of eighth subculture by using both RAPD (41.61%) and ISSR (31.65%) markers. The SPAR method ensured that the present protocol may be used for true to type plant production up-to five consecutive subcultures.

Physical and biochemical characterization of freeze-dried Aloe vera L. gel (AG) has been carried out from different age groups and harvesting seasons to get a clear scenario of AG properties at different growth periods. The stability of amorphous AG under thermal perturbation was analyzed with reference to the respective glass transition temperature by differential scanning calorimetry. The functional properties of gel in the form of water holding and fat adsorption capacity were more pronounced at 3-year-old plants in summer. A higher glass transition temperature (135 ± 4.80 °C) of gel from 3-year-old aloe accounts for higher concentration and better cross-linking of the component polysaccharides. The chemometric studies encompassing principal component and partial least square analysis depict an intrinsic structure-function relation with reference to different properties considered, which has been demonstrated to be influenced by growth periods of plants.

This paper presents an analysis of elemental distribution, microstructure at pre- and post-rehydration, and swelling of freeze-dried Aloe vera L. gel, obtained from two, three and four-year-old plant in summer. To explore the seasonal influence, three-year-old plants from rainy and winter season are also considered for analysis. Mineral distribution is studied following the estimation of Ca, K, Mg, P, Na, Mn, Se, Al, Fe, Zn, Cu and Cd. A consolidated effort has also been made to study the concentration of total C and N content of gel at different growth periods. Re-hydration mediated continuous topography in poly-dispersed, unorganized and amorphic freeze-dried gel accounts for the post-rehydration cross-linking among the component polysaccharides. Chemometric analysis (principal component and cluster analysis) suggests that the mineral content of gel change as a function of growth periods of plants. High content of organic C and Se with maximum water absorbing potential (in the form of swelling activity) are mainly associated with three-year-old aloe of summer; the contents of N, Na, Ca, K, Mg, P and Cu are observed to be high in two-year plants. To the best of our knowledge and belief, this is the first time, Se (a bioactive antioxidant activity promoting element) is found to be present in aloe gel.

Various free radicals (DPPH, super-oxide and hydroxyl) scavenging, transition metal chelating and reducing power assays were conducted to study the antioxidant potential of freeze-dried foliar gel obtained from 2, 3 and 4-year-old Aloe vera L. To explore the influence of season, apart from summer, gels from rainy and winter season of 3-year-old aloe were also considered. Gels obtained from different growth periods showed antioxidant potential with varying free radical quenching, transition metal chelating and reducing power activity. The antioxidant activity of aloe gel is changed as a factor of the age of the plants and harvesting seasons, and found to be more pronounced in 3-year-old aloe during summer. Degree of acetylation and functional group distribution studied by 1H NMR and FTIR spectroscopy respectively, and the distribution of the component polysaccharides and phenolics at different harvesting regimens are found to be critical in the regulation of bioactive potential of aloe gel in terms of pertained antioxidant activity.

Antioxidant assay, ATR-FTIR spectroscopy mediated predominant functional group detection and UV-absorption spectroscopy have been carried out with methanolic extracts of Aloe vera L. gel (gel-extract) from two, three and four-year-old plants in summer season. To explore the seasonal influence gel-extract has also been prepared from three-year-old aloe in rainy and winter season. Gel-extracts from three-year-old aloe in winter exhibited high response at IR and UV absorption spectrum. Maximum transmittance in IR spectrum has been assigned to phenolic OH stretching followed by C H, CO and COC. Total phenols, flavonoids and flavonols content range from 30.11 ± 1.89 to 35.77 ± 1.07 μg GAE/mg, 11.00 ± 0.88 to 29.75 ± 0.88 μg RE/mg and 7.47 ± 0.31 to 13.87 ± 0.08 μg RE/mg, respectively. The contents of total phenolics, flavonoids, flavonols, aloin, and different free radical scavenging, transition metal chelating and Fe3+ reducing are more pronounced in the gel-extracts from three-year-old aloe at winter and summer season. Phenolics concentration and the distribution of aloin in the gel-extract are significantly (p ≤ 0.05) influenced by the growth periods of A. vera. The presence of conjugated double bonds and high abundance of the integral phenolic OH attribute to the UV absorption and antioxidant potential of the gel-extract, respectively. The present work analysis shows that growth periods of A. vera plays a decisive factor in the regulation of antioxidant activity and UV absorption property of the gel-extracts.

Congo-red-acemannan (CR-acemannan) binding assay has been followed to compare the acemannan distribution in freeze-dried gel at two, three and four-year-old Aloe vera L. To explore the seasonal influence gels are also analyzed at rainy and winter season from three-year-old plants. Detection of predominant functional groups and elemental analysis have been carried out by ATR-FTIR and SEM-EDS, respectively. SEM and L * a * b * color space analysis have been employed to explore the microstructure and appearance of freeze-dried gel, respectively. Acidity and electrical-conductivity have also been measured as the physical properties of gel. Electrical-conductivity was significantly high ( p ≤ 0.05) at two-year-old plants and all of the gels are acidic in range (4.63 ± 0.02 to 4.93 ± 0.01). From 1 H NMR spectroscopy, no sign of retrogradation was noticed in dried gel. It has been observed that growth periods play the decisive factor influencing the acemannan and mineral concentration, and the color components of freeze-dried gel as well. Of the tested freeze-dried gels, the absorbance specific to CR-acemannan conjugate formation is maximum with three-year-old plants in summer, and minimum with two-year-old plants. Phenolic OH, CO, CH 3 , COO and C O C are the predominant functional groups present in gel. Collectively, sodium concentration was high in gel followed by magnesium, potassium and calcium. Among the considered minerals, the relative abundance is more with Mg, K and P at two-year-old Aloe . Sublimation at freeze-drying renders an unorganized dispersed structure to aloe gel by breaking down the compact parenchymatous cellular structure. Our experiments suggest that, the lightness of gel is high in winter, followed by summer, for a three-year-old plant.