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6-C-prenyl luteolin, a new naturally occurring compound, together with luteolin 5,3′-dimethyl ether, luteolin 5-glucoside and luteolin 3′-glucoside were isolated from callus of Hypericum perforatum var. angustifolium . These flavonoids were completely different from those previously observed in in vivo plants of the same species. The total flavonoid content of callus , around 0.5–0.7 mg g −1 dry wt, was much lower than that found in wild growing Hypericum perforatum plants (14–70 mg g −1 dry wt).

From spinach leaves (cv Viroflay), five new naturally occurring flavonoids have been isolated and identified by 13 C NMR, 1 H NMR, FAB-MS, UV and hydrolytic and enzymatic procedures. The new compounds were identified as spinacetin 3- O -β- d -glucopyranosyl(1 → 6)-[β- d -apiofuranosyl(1 → 2)]-β- d -glucopyranoside, patuletin 3- O -β- d -(2″feruloylglucopyranosyl)(1 → 6)-[β- d -apiofuranosyl(1 → 2)]-β- d -glucopyranoside, spinacetin 3- O -β- d -(2″- p -coumaroylglucopyranosyl)(1 → 6)-[β- d -apiofuranosyl(1 → 2)]-β- d -glucopyranoside, spinacetin 3- O -β- d -(2″feruloylglucopyranosyl)(1 → 6)-[β- d -apiofuranosyl(1 → 2)]-β- d -glucopyranoside and spinacetin 3- O -β- d -(2″feruloylglucopyranosyl)(1 → 6)-β- d -glucopyranoside. The known compounds jaceidin 4′-glucuronide, 5,3′,4′-trihydroxy-3-methoxy-6:7-methylenedioxyflavone 4′-glucuronide, 5,4′-dihydroxy-3,3′-dimethoxy-6:7-methylenedioxyflavone 4′-glucuronide, patuletin 3-glucosyl(1 → 6)-[apiosyl(1 → 2)] glucoside and patuletin and spinacetin 3-gentiobiosides, were also detected. © 1997 Elsevier Science Ltd. All rights reserved

Seven flavonols were isolated and identified from Pisum sativum (cv Solara) shoots. The 3-glucoside, and 3-sophorotrioside [beta-D-glucopyranosyl(1-->2)-beta-D- glucopyranosyl(1-->2)-beta-D-glucopyranoside] of quercetin, the 3-sophorotrioside of kaempferol, and the acylated derivatives of quercetin 3-sophorotrioside with p-coumaric, caffeic, ferulic and sinapic acids on the hydroxyl at the 6-position of the terminal sugar. The caffeic and sinapic acid esters are two new naturally occurring compounds. This is the first report in which the structures of the p-coumaryl- and ferulyl-sophorotriosides of quercetin, which were previously reported from pea leaves, have been completely established by means of 1H NMR studies including COSY, NOESY and TOCSY experiments.

Two distinct flavonoid patterns have been found in plants of Gratiola officinalis which are not correlated with morphological differences. One of the chemotypes is characterized by the production of 8-hydroxylated flavone O -glycosides, among which are the new plant substances 8-hydroxychrysoeriol 8- O -glucuronide, hypolaetin 7- O -sophoroside, 8-hydroxychrysoeriol 7- O -sophoroside and isoscutellarein 8- O -sophoroside. The flavonoids of the other chemotype are lacking 8-hydroxylation, but some are hydroxylated in the 6-position. Both chemotypes are similar to each other in that they also contain flavone C -glycosides, a class of flavonoid which is rare in the Scrophulariaceae.

The phenolic compounds present in 38 propolis samples produced in tropical Venezuela by imported Apis mellifera and five indigenous species of stingless bees, and seven propolis samples from different temperate regions were analysed by HPLC. The different tropical propolis generally showed a single phenolic profile characterized by the occurrence of polyprenylated benzophenones as major components. Flavonoids were present in only a few samples, and in each case they were found to be lipophilic methylated 6-oxygenated flavones (eupatorin, hispidulin, 5-hydroxy-6,7,3′,4′-tetramethoxyflavone, etc.). Generally, no correlations between the composition of tropical propolis and the place of collection or the bee species were found. However, propolis from temperate areas contained flavonoids (with an unsubstituted ring B) as the main phenolic components (pinobanksin, pinobanksin 3-acetate, pinocembrin, chrysin, galangin and tectochrysin). These analyses confirmed that the source of the phenolics found in propolis produced in temperate regions was different Populus species of section Aigeiros (Salicaceae). The resins exuded by the flowers of Clusia minor and C. major (Guttiferae) contained the polyprenylated benzophenones found in the majority of the propolis studied, suggesting that this is the main source for propolis in tropical Venezuela.

The occurrence of flavonoid p -coumaroylglucosides and 8-hydroxyflavone 7-allosylglucosides is restricted, in the Labiatae, to some genera of subfamily Lamioideae (tribe Stachydeae). Generally both types of compounds do not co-occur in the same species. Thus, flavonoid p -coumaroylglucosides are present in all the species studied of the genera Ballota , Phlomis and Marrubium , and are universally present in the subgenus Marrubiastrum of Sideritis , in subgenus Galeopsis and in section Betonica of genus Stachys , while 8-hydroxyflavone 7-allosylglucosides accumulate in the other Sideritis , Stachys and Galeopsis species. Amongst the flavonoid p -coumaroylglucosides, the apigenin derivatives occur most frequently but also the corresponding luteolin, chrysoeriol, kaempforol and isorhamnetin glycosides have been detected. The 8-hydroxyflavone allosylglucosides occur as such and also as the monoacetylated and diacetylated derivatives. The presence of p -coumaroylglucosides and/or 8-hydroxyflavone allosylglucosides shows the affinities of Anisomeles , Pogostemon , and Leonurus species with Ballota , Marrubium , Phlomis , Sideritis , Stachys and Galeopsis species. These results suggest that flavonoid p -coumaroylglucosides are valuable markers for chemotaxonomic studies.

A phytochemical study of the flavonoid glycosides present in the aerial parts of Galeopsis angustifolia has shown the existence of hypolaetin, isoscutellarein and hypolaetin 4′-methyl ether 7- O -β- d -(2″- O -β- d -allosyl)glucosides as well as their mono- O -acetylated and di- O -acetylated derivatives in the sugar moiety. The distribution of these compounds in different Galeopsis species has been studied by reversed-phase HPLC. This survey shows that the 8-hydroxyflavone glycosides are confined to subgenus Ladanum while subgenus Galeopsis accumulates luteolin, apigenin and scutellarein 7- O -β- d -glucuronides and p -coumaroyl glucosides of apigenin and luteolin instead.

23 pages, 2 tables., Epidemiological studies show a link between the consumption of plant-derived foods and a range of health benefits. These benefits have been associated, at least partially, to some of the phytochemical constituents, and, in particular, to polyphenols. In the last few years, nutraceuticals have appeared in the market. These are pharmaceutical forms (pills, powders, capsules, vials, etc.) containing food bioactive compounds as active principles. The bioactive phytochemicals have become a very significant source for nutraceutical ingredients. Scientific research supports the biological activity of many of these food phytochemicals, but the health claims attributed to the final marketed nutraceutical products have often little or doubtful scientific foundation. This is due to the fact that a lot of the scientific evidence is derived from animal testing and in vitro assays, whereas human clinical trials are scarce and inconclusive. Some key issues such as bioavailability, metabolism, dose/response and toxicity of these food bioactive compounds or the nutraceuticals themselves have not been well established yet. Amongst the phytochemicals, several groups of polyphenols (anthocyanins, proanthocyanidins, flavanones, isoflavones, resveratrol and ellagic acid) are currently used in the nutraceutical industry. In this report, we have reviewed the most recent scientific knowledge on the bioavailability and biological activity of these polyphenols (‘fact’), as well as the health claims (which are not always supported by scientific studies) ascribed to the polyphenols-containing nutraceuticals (‘fiction’). The in vitro antioxidant capacity, often used as a claim, can be irrelevant in terms of in vivo antioxidant effects. Bioavailability, metabolism, and tissue distribution of these polyphenols in humans are key factors that need to be clearly established in association to the biological effects of these polyphenols-containing nutraceuticals. The future trends of phytochemistry research regarding nutraceuticals are discussed., [Graphical abstract]:Nutraceuticals are pharmaceutical forms containing food phytochemicals as active principles. Scientific research supports the biological activity of many of these food phytochemicals, but the health claims attributed to the marketed nutraceuticals have often doubtful scientific foundation. Bioavailability and metabolism are key factors to understand the biological effects of these nutraceuticals., The authors are grateful to the Spanish MEC and to Feder funds for support of this work (AGL2004-03989).

From Cistus ladanifer bee pollen 12 flavonoid glycosides and four aglycones have been isolated and identified. They are glycosides of myricetin, quercetin, isorhamnetin and kaempferol. Quercetin and isorhamnetin 3-xylosyl(1 → 6)glucosides are new naturally occurring flavonoids. This complex flavonoid pattern contrasts with those of almond and rosemary bee pollens which are rather simple and characterized by the presence of only two or three flavonoids. These results support the use of flavonoid analysis in the determination of the botanical origin of bee pollen.

From the aerial parts of Helichrysum decumbens , H. stoechas and H. italicum , antibacterial (anti-gram positive) phloroglucinol and acetophenone derivatives have been identified. Phloroglucinol derivatives showed eight times more antibacterial activity (MIC 12.5 μg/ml) than the acetophenone derivative, but the latter was also active against gram negative bacteria ( Escherichia coli ). Both types of compounds showed antifungal activity against different fungi ( Penicillium sp., Cladosporium herbarum and Phythophtora capsicii ) but proved to be inactive against Aspergillus species at MIC of 100 μg/ml. These results confirm that the co-occurrence of acidic phenolic hydroxyls and lipophilic residues is an important chemical feature for the expression of antifungal activity.

From the stem bark of the halophytes Tamarix gallica , T. africana and T. bobeana , the new compound coniferyl alcohol 4-sulphate was isolated and identified by UV, IR, FAB-MS, 1 H and 13 C NMR techniques. Other cinnamyl alcohol sulphates were detected but their structures were not fully established. Phenolic sulphates were also present in other tissues of these plants. Coniferyl alcohol sulphate was found in another halophyte, Arthrocnemum fruticosum (Chenopodiaceae) suggesting that it could be a common storage precursor of lignin in woody halophytes. In addition, kaempferol 4′-methyl ether 3-sulphate, a new naturally occurring compound, and tamarixetin 3-sulphate were identified in the stem bark of the three Tamarix species.

The flavonoids, both external aglycones and vacuolar flavonoid glycosides, have been identified in the aerial parts of endemic North African Sideritis species. The flavonoids produced by these African species are very similar to those produced by Spanish species, being mainly 7-allosylglucosides of 8-hydroxyflavones. Two new flavonoid glycosides, apigenin and luteolin 7-allosylglucosides, have been identified in these plants. Species of the section Sideritis are characterized by the accumulation of the 7-glycosides of 8-hydroxyflavones (isoscutellarein, hypolaetin and their methyl ethers) whereas those of section Hesiodia accumulate 7-glycosides of the common flavones (apigenin, luteolin and chrysoeriol).

A leaf survey of 308 species belonging to the Labiatae, Scrophulariaceae and to five related families has shown that the common flavones, apigenin, luteolin and chrysoeriol are widely present, occurring especially as the 7-glucuronides. In addition 48 species (16% of sample) contain 8-hydroxyflavones and 131 species (43%) 6-hydroxy- or 6-methoxyflavones in glycosidic combination. The frequencies recorded are slightly higher than those found (35% for both groups) in earlier surveys. 8-Hydroxyflavones based on apigenin and luteolin are restricted to the Labiatae (5 genera), Scrophulariaceae ( Gratiola and Veronica ) and Lentibulariaceae ( Pinguicula ). In Labiatae, they only occur in the subfamily Lamoideae and not in the Nepetoideae. In Veronica , they are restricted to species in the sections Alsinebe and Chamaedrys . 6-Oxygenated flavones have a more sporadic distribution, but are consistently present in genera such as Scutellaria , Phlomis , Micromeria , Origanum and Thymus (Labiatae), in Parahebe (Scrophulariaceae) and Globularia (Globulariaceae). Although uncommon, flavonol glycosides were detected in a few species of the Labiatae, Scrophulariaceae and Globulariaceae, and C -glycosylflavones were detected in a few species of the former two families. The chemosystematic significance of these findings is discussed.

From the aerial parts of the maritime plant Lippia nodiflora , 15 flavonoids, 3 flavone aglycones and 12 new flavone sulphates, have been isolated and identified. The new flavone sulphates are mono- and disulphates of nepetin, jaceosidin, hispidulin, 6-hydroxyluteolin and nodifloretin present as the sodium salts. These sulphates are the only flavone conjugates detected in this plant. Flavone trisulphates are additionally present in populations of this species from Malaysia and Saudi Arabia, but lack of plant material prevented their complete characterization. Analysis of the closely related species Lippia canescens showed that it has the same flavonoid pattern. By contrast, a third species L. triphylla showed a flavonoid pattern lacking flavonoid sulphates, but characterized by the presence of 7-glucuronylglucosides of luteolin, diosmetin and apigenin. This is the first finding of flavonoid sulphates in the Verbenaceae.

A survey of aerial tissues of 42 European taxa of the genus Teucrium has revealed the widespread presence of five surface flavonoids: cirsiliol, cirsimaritin, cirsilineol, salvigenin and 5-hydroxy-6,7,3′,4′-tetramethoxyflavone. The latter two compounds are useful taxonomic markers in that salvigenin is characteristic of species of section Polium, while 5-hydroxy-6,7,3′,4′-tetramethoxyflavone is completely confined to species of the other five sections surveyed. Eleven flavone glycosides, four flavonol glycosides and the glycoflavone vicenin-2 were found to occur as vacuolar constituents. One of the flavone glycosides, cirsimaritin 4′-glucoside, only occurs in the species T. arduini, while two others, hypolaetin and isoscutellarein 7-acetyl-allosylglucosides, are characteristic of the closely related T. chamaedrys and T. webbianum. 6-Hydroxyluteolin is widely present as the 7-glucoside and 7-rhamnoside, the latter compound being a new glycoside. In general, the chemical results are correlated with sectional classification and usefully indicate that at least one taxon, T. compactum, is misplaced within the genus. Phyletically, the restriction of flavonol glycosides mainly to section Teucrium suggests that this may be the basic group within the genus.

In addition to the previously characterized amentoflavone and dihydroamentoflavone, two further biflavonoids have been identified from Isophysis tasmanica : hinokiflavone and podocarpusflavone A. This is the first time these two biflavonoids have been found in the monocotyledons. Amentoflavone has also been discovered in Xerophyta plicata ; this constitutes the first record of biflavonoids in Velloziaceae.

From the aerial parts of Helichrysum decumbens , three new antifungal phloroglucinol derivatives have been identified. Their structures have been established by UV, IR, EIMS, FAB-MS, 1 H NMR and 13 C NMR techniques. In addition, the highly methylated flavonoids 3,5-dihydroxy-6,7,8-trimethoxyflavone, 5,7-dihydroxy-3,6,8-trimethoxy-flavone and 3,5-dihydroxy-6,7-dimethoxyflavone have been detected, the latter being a new naturally occurring compound. The phloroglucinols prevented the growth of Cladosporium herbarum in a bio-assay. These secondary metabolises are externally deposited on the plant surfaces.

The occurrence of interspecific hybrids of Sideritis angustifolia and S. incana has been biochemically verified by TLC and HPLC analyses of external and internal flavonoids. A correlation between the excretion of flavonoids and the presence of glands in the taxa studied has been observed. The hybrids produce flavonoid patterns which contain the substances typical of both parents.

From the aerial parts of Helichrysum nitens , 5,7-dimethoxyflavone, 5,6,7-trimethoxyflavone, 3,5,7-trimethoxyflavone, 5,6,7,8-tetramethoxyflavone, 3,5,6,7-tetramethoxyflavone and 3,5,6,7,8-pentamethoxyflavone have been isolated and identified. In addition, 5-hydroxy-6,7-dimethoxyflavone and 5-hydroxy-6,7,8-trimethoxyflavone have also been found. The antifungal activities of the fully methylated compounds were similar to that of tangeretin (5,6,7,8,4′-pentamethoxyflavone), an antifungal flavonoid isolated from Citrus leaves. These compounds have been found externally deposited on the leaf and stem surfaces. 3,5,6,7,8-Pentamethoxyflavone is a new naturally occurring flavonoid.

The novel flavonol 8-methoxykaempferol 3-O-(2″-β- d -glucopyranosyl-β- d -glucopyranoside) has been found as a yellow pigment in almond pollen. In addition, trace amounts of kaempferol and quercetin 3-diglucosides have been detected. These compounds have been isolated from almond bee pollen, which is a convenient source for the study of flavonoids from natural pollen. HPLC studies show no differences in the flavonoid patterns of pollen and bee pollen, and demonstrate that 8-methoxykaempferol 3-sophoroside is the main flavonoid in almond pollen, while other flower and leaf tissues are devoid of this pigment. This compound is also absent from other botanically related pollens (plum, apple, cherry, and pear).

The pigments of Salvia splendens flowers (scarlet cvs) have been identified as pelargonidin 3-caffeoylglucoside-5-dimalonylglucoside and pelargonidin 3-p-coumaroylglucoside-5-dimalonylglucoside. The flowers of S. coccinea contain the same pigments in the corolla but the calyx contains, in addition, the cyanidin analogues.