THE POLYPHENOLICS AND FLAVONOIDS OFHARPEPHYLLUM CAFFRUM

Abstract

The study of the polyphenolics and flavonoids of Harpephyllum caffrum resulted in the isolation of protocatechuic acid, gallic acid, methyl gallate, kaempferol-3-rharnnoside, kaempferol-3-galactoside, apigenin-7-glucoside, quercetin-3-rhamnoside, quercetin-3-glucoside, quercetin-3-arabinoside . and the free aglycones quercetin and kaempferol.It has been reported that the tannins of Harpephyllum caffrum belong to the condensed class of tannins (SALEH et al. 1969). It has also been pointed out that H. caffrtrm is used as a tanning material in South Africa, with its leaves and bark containing 11% and 18% tannins respectively (WILLIAMS 1930). T h e leaves of H. caffrum growing in Egypt contain 14% tannins (EL SHERBEINY et al. 1973). Flavandiols are the only plant constituents reported so far in H. caffrum bark by Roux and EVELYN (1958) The present study deals with the separation and identification of the leaf polyphenolics and flavonoids of H. caffrum growing in Egypt.The fresh leaf material was extracted with 70% ethanol. The ethanol extract was fractionated by column chromatographic technique, using polyamide powder and watedmethanol mixtures of decreasing polarity.Paper chromatography of the fractions eluted with 30% methanol revealed the presence of protocatechuic acid, gallic acid and methyl gallate.The glycosidic fraction was eluted from the column with 40-70% methanol and revealed by two-dimensional paper chromatograms to contain six glycosides (GI-Gd.The last fractions were eluted with 90% methanol and proved to contain the flavonols quercetin and kaempferol.Attempts were made to separate the six glycosides of the glycosidic fraction applying polyamide column chromatography eluted with a mixture of benzene/ ethanouwater (60:38:2). The column only succeeded in separating two glycosides which were identified as kaempferol-3-rhamnoside (afizelin) (GI) and apigenin-7-glycoside ( G e ) .The remaining glycosides were separated applying elution technique on TLC Downloaded by: National University of Singapore. Copyrighted material.

Structure and antioxidant activity of phenolic compounds isolated from the edible fruits and stem bark ofHarpephyllum caffrum

“…[21] The presence of these compounds in H. caffrum has not previously been reported. The flavonoids, quercetin and kaempferol, that were previously identified by TLC in this plant by El Sherbeiny and El Ansari [6] were not found in this study. However, the flavan-3-ol, (C)-catechin, was found as one of the major compounds in the plant.…”

“…The total reducing power of the isolated compounds from H. caffrum was determined according to the ferric reducing antioxidant power (FRAP) method as described by Ferreira et al [11] Working solutions of the isolated compounds were prepared in DCM or MeOH in 10 mL volumetric flasks from 10 mg mL ¡1 stock solutions to obtain two-fold dilutions ranging from 250.00 mg mL ¡1 to 15.63 mg mL ¡1 . Exactly 2.50 mL of the sample solutions were mixed with 2.50 mL of phosphate buffer solution (0.20 M, pH D 6.6) and 2.50 mL of 1% potassium ferricyanide [K 3 Fe(CN) 6 ] solution in test tubes and placed in a water bath at 50 C for 20 min. Thereafter, 2.50 mL of 10% trichloroacetic acid (TCA) was added to the mixture, of which 2.50 mL was pipetted into a flask containing 2.50 mL distilled water and 0.50 mL of 0.1% FeCl 3 solution and allowed to stand for 10 min.…”

“…[5] The organic constituents of H. Caffrum are not well known, but ethanolic extracts from the leaves have been reported to contain protocatechuic acid, gallic acid, methyl gallate, quercetin, and kaempferol, based on relatively simple techniques such as thin layer chromatography and UV spectroscopy. [6] Other trees belonging to the same family include mango (Mangifera indica), African resin tree (Ozoroa insignis), M'Peku (Lannea velutina), and cashew nut (Anacardium occidentale). Compounds isolated from these trees include anacardic acid, cardols, cardanols, flavonoids, and triterpenoids.…”

Antibacterial and antifungal activity of traditional medicinal plants used against venereal diseases in South Africa

“…The ethyl acetate extract showed slight activity. Harpephyllum caffrum is reported to contain phenolic compounds which may be responsible for its biological activity (El Sherbeiny and El Ansari, 1976).…”

Bioactive constituents from Harpephyllum caffrum Bernh. and Rhus coriaria L

“…Previous phytochemical work on H. caffrum indicated a brief note on a tentative identification of afzelin, quercetin-3-O-β-arabinoside, apigenin-7-O-α-glucoside, kaempferol-3-O-β-galactoside, kaempferol, and quercetin. [9] H. caffrum stem bark extract was previously evaluated for the total polyphenol content and antioxidant activity. [10] Phenolic constituents of Sumac were dealt with in previous reports.…”