Jenny Greenham

Chrysin and other leaf exudate flavonoids in the genus Pelargonium

In a chemotaxonomic survey of 57 Pelargonium species, leaf exudate flavonoids were detected in 35% of the sample, mostly in trace amounts. However, chrysin and a related C-methylflavanone were identified as major leaf surface constituents of P. crispum, and a mixture of quercetin and kaempferol mono-, and di- and trimethyl ethers of P. quercifolium. In two other species, P. fulgidum and P. exstipulatum, methylated flavones were the only lipophilic flavonoids present. This is the first report of leaf surface flavonoids from the genus Pelargonium.

Condensed tannins and sugars in the diet of chimpanzees (Pan troglodytes schweinfurthii) in the Budongo Forest, Uganda

Abstract Fruits, leaves and bark forming part of the diet of chimpanzees were collected and it was noted whether samples were of a kind being eaten or not eaten. Samples were dried and analysed for condensed tannin content and for three sugars, glucose, sucrose and fructose. It was found that chimpanzees did not select foods according to the level of tannins but did so according to the levels of sugars, preferring the higher levels. Fig seeds contained higher tannin levels than fig pulp, and the chimpanzees made oral boli (“wadges”) of fig seeds which they spat out. Two fig species were compared: the one with lower tannin and higher sugar content was preferred. The bark of one tree species often eaten contained high levels of tannins but also contained sugars. Young leaves with lower tannin levels were preferred to mature leaves with higher levels. Chimpanzees appear to be able to tolerate higher tannin levels than three monkey species in this forest, and considerably higher levels than marmosets (Callitrichidae).

Distribution of charged flavones and caffeylshikimic acid in Palmae

Identification of the phenolic constituents in flowers of nine palm species has revealed that charged C-glycosylflavones and caffeylshikimic acid are characteristically present. Flavonol glycosides are also common; the 3-glucosides, 3-rutinosides and 3,4′-diglucosides of quercetin and isorhamnetin and the 7-glucoside and 3,7-diglucoside of quercetin are all variously present. Tricin 7-glucoside, luteolin 7-rutinoside and several unchanged C-glycosylflavones were also detected. Male flowers of Phoenix canariensis differ from female flowers in having flavonol glycosides. As expected, in most species studied, flavonoid patterns in the flowers vary considerably from those found in the leaves.

Ten isoprenylated and C-methylated flavonoids from the leaves of three Vellozia species

Abstract Eight new and two known lipophilic flavonoids were isolated from the leaf surface of Vellozia coronata, V. glabra and V. nanuzae. Four are flavanones: velloeriodictyol [2″-isopropenyldihydrofurano(4″,5″:6,7)-eriodictyol], 6,8-diprenyleriodictyol, 6-(3-hydroxyisopentanyl) eriodictyol and 6-C-methyleriodictyol 7,3′,4′-trimethyl ether. Two are flavonols, the 6-prenyl derivatives of quercetin 3-monomethyl ether and of quercetin 3,7-dimethyl ether. Two new C-methyl ethers, namely 8-C-methylquercetagetin 3,6,3′-trimethyl ether and 8-C-methyl-6-hydroxykaempferol 3,6,7-trimethyl ether, were accompanied by the known 3,6,7-trimethyl ether and 3,6,7,3′-tetramethyl ether of 8-C-methylquercetagetin. Also present in the lipophilic fraction is a resveratrol dimethyl ether mixture, which has considerable antifungal activity. The vacuolar flavonoids of the same three Vellozia species were variously identified as tricin 5-glucosisde, five orientin-based C-glycosides, the 7-glucoside and 7-rhamnosylglucoside of 6-hydroxyluteolin, the 7-glucoside of pleurostimin and the 6-glucoside of its 7-methyl ether. The chemosystematic significance of these findings is briefly discussed.

Acylated anthocyanins and flavonols from purple flowers of Dendrobium cv. ‘Pompadour’

Abstract Two rare anthocyanins, cyanidin 3-(6-malonylglucoside)-7,3′-di(6-sinapylglucoside) and the demalonyl derivative, were characterised as the purple floral pigments of Dendrobium cv. ‘Pompadour’. Nine known flavonol glycosides were also identified, including the 3-rutinoside-7-glucosides of kaempferol and quercetin. One new glycoside was detected: the ferulyl ester of quercetin 7-rutinoside-7-glucoside. These flavonoid patterns are typical for plants in the family Orchidaceae.

Variations in the lipophilic and vacuolar flavonoids of the genus Vellozia

Abstract Five lipophilic flavonoids were identified in Vellozia aff. scoparia : kaempferol, kaempferol 3-methyl ether, luteolin, chrysoeriol and a new compound, 6-prenylherbacetin 3,8-dimethyl ether. Five such substances were identified in V. phalocarpa : luteolin, chrysoeriol, eriodictyol, 6- C -methylquercetin 3-methyl ether and 8- C -methylquercetagetin 3,6,7,4′-tetramethyl ether. Five compounds were identified in V. laevis : velloquercetin 3,3′-dimethyl ether, 8- C -methyl-6-hydroxykaempferol 3,6,7-trimethyl ether and the 3,6,7,3′- and 3,6,7,4′-tetramethyl ethers of 8- C -methylquercetagetin. A method for distinguishing these latter two isomers is described. All three species also contained a range of vacuolar flavone O - and C -glycosides; two contained a new conjugate of orientin, the 7-caffeate. These lipophilic and vacuolar flavonoid patterns were compared with those of seven other Vellozia species and the results used to prepare similarity indices within the genus. Although all 10 species have distinctive profiles, there is no evidence to suggest that any of these species should be transferred to a different genus.

DIFFERENCES IN FLAVONOID PATTERNS BETWEEN GENERA WITHIN THE VELLOZIACEAE

Abstract Detailed flavonoid analysis of seven representative species of Aylthonia , Barbacenia , Burlemarxia and African and Madagascan Xerophyta have confirmed the paucity of surface flavonoids in these genera compared with Vellozia , where complex mixtures of lipophilic flavonoids are common. However, some simple flavonol O -methyl ethers including 6-methoxykaempferol 3- O -methyl ether were found in small amounts on the leaf surface of two Barbacenia species. In the subfamily Barbacenioideae, Aylthonia was distinguished from both Barbacenia and Burlemarxia in its vacuolar flavonoids by the presence of flavone mono- C -glycosides rather than flavone di- C -glycosides and Pleurostima is unique in lacking glycoflavones but possessing 6-hydroxyflavones. Complex mixtures of flavonol mono- O - and di- O -glycosides were found within the leaves of Barbacenia and Burlemarxia species, while only quercetin monoglycosides were detected in Aylthonia riedeliana . In Barbacenia conicostigma , the 3-apiosylgalactosides and 3-apiosylglucosides of quercetin and isorhamnetin were characterized; the former two compounds were present also in Burlemarxia spiralis . In Xerophyta eglandulosa var. eglandulosa from Madagascar an isomeric quercetin 3-apiosylglucoside occurred. The Madagascan Xerophyta species were distinguished from the African Xerophyta species by the absence of glycoflavones and presence of isorhamnetin glycosides, while in X. dasylirioides quercetin 3-methyl ether and quercetin di- and trimethyl ethers were identified free within the leaf. Similarly, in Barbacenia conicostigma four flavonol methyl ethers, as well as kaempferol and chrysoeriol occurred in the free state. However, X. retinervis from South Africa was exceptional in producing 6- C -methyl quercetin 3-methyl ether, chrysoeriol 7-glucoside and both flavone mono- and di- C -glycosides within the leaf. The present results confirm that flavonoid patterns are useful in determining generic limits within the family.

Correlations between leaf flavonoids, taxonomy and plant geography in the genus Disporum

Abstract In a flavonoid survey of 10 Disporum species using hydrolysed leaf extracts, the flavonols quercetin and kaempferol were found to be the main constituents of five North American species while in the five Asian taxa the flavone luteolin was the main component with some apigenin and chrysoeriol. This clear chemical difference supports the geographical division of Disporum into two sections and possibly into two genera with the re-erection of the genus Prosartes for the North American species. This was further supported by a more detailed analysis of the flavonoid glycosides in four taxa, which showed 16 chemical differences between North American and Asian plants. A number of unusual flavone glycosides were identified including luteolin 4′-mono- and 4′-diglucosides, apigenin 4′-diglucoside, a luteolin 4′-rhamnosylglucoside and luteolin and apigenin 7,4′-diglucosides. Within the Asian taxa most species have distinct flavonoid profiles. However, there is good evidence of chemical polymorphism in the D. cantoniense-D. sessile group. Thus, at least three distinct flavonoid patterns occur amongst the different accessions of D. cantoniense from China and the Himalayas. But more surprisingly, the Japanese species D. sessile is chemically indistinguishable from some specimens of D. cantoniense even though the two species are morphologically distinct, suggesting there might have been a common ancestor for the two species before the division of the present land masses.

Six further lipophilic flavonols from the leaf of Vellozia stipitata

Abstract Six new lipophilic flavonols have been characterized from the leaf of Vellozia stipitata: vellokaempferol 3,5- dimethyl ether, velloquercetin 3-methyl ether and 3,5,3′-trimethyl ether, 8-C-methylvellokaempferol 3,5-dimethyl ether, 8-C-methylvelloquercetin 3-methyl ether and 3,5,3′-trimethyl ether. A seventh compound present is identical to 5,4′-dihydroxy-3,6,7,3′-tetramethoxy-8-C-methylflavone, recently detected in V. lilacina and V. aff. epidendroides. Vacuolar flavonoids in the leaf include iso-orientin 7-glucoside, iso-orientin, an orientin O-glucoside and a vicenin derivative. This pattern of flavonoid accumulation is compared with that present in the leaf of V. streptophylla.

Occurrence of C-methylflavonols in leaves of Vellozia

Abstract Two new C-methylflavonols have been identified in the leaves of Vellozia lilacina and V. aff. epidendroides. They are 5,3′,4′-trihydroxy-3,6,7-trimethoxy-8-C-methylflavone and the corresponding 3′-methyl ether. This is the first report of C-methylflavonols in the Velloziaceae and the third finding of such compounds in monocotyledonous plants. Tricin 5-glucoside, luteolin, orientin, iso-orientin and iso-orientin 7-apioside were also identified in these two plants.