A new cyclohexenone (1) and a new caffeoyl ester derivative (2), together with the known compounds (-)-isolariciresinol 3-alpha-O-beta-D-glucopyranoside (3), (+)-1-hydroxypinoresinol 1-O-beta-D-glucopyranoside (4), isoacteoside (5), luteolin 4'-O-beta-D-glucopyranoside (6), and indole-3-carboxylic acid (7), were isolated from the leaves of Bauhinia tarapotensis. The structures of these new compounds were determined by spectroscopic data analysis. The antioxidant activities of 1-7 were determined by measuring their free radical scavenging effects, using the 1,1-diphenyl-2-dipicrylhydrazyl free radical (DPPH) and Trolox equivalent antioxidant activity (TEAC) methods, and the coupled oxidation of beta-carotene and linoleic acid. Compounds 3-5 showed good activities in the DPPH and TEAC tests, while compounds 1 and 2 were active in the coupled oxidation of beta-carotene and linoleic acid bioassay.

Antioxidant principles from Bauhinia tarapotensis.

Ten phenolic compounds were isolated from a butanol fraction of sage extracts. Their structures were determined by spectral methods (NMR, MS, IR). Among them, a novel compound, 4-hydroxyacetophenone-4-O-β-d-apiofuranosyl-(1→6)-O-β-d-glucopyranoside, was identified. Two test systems, DPPH free radical scavenging activity and radical cation ABTS•+ scavenging activity, were used to evaluate their antioxidant activity. The most active compounds were found to be rosmarinic acid and luteolin-7-O-β-glucopyranoside. Keywords: Sage; Salvia officinalis; phenolic compounds; antioxidant activity

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Antioxidative Phenolic Compounds from Sage (Salvia officinalis)

One hundred fifty-two methanol and water extracts of different parts of 71 plants commonly used in Sudanese traditional medicine were screened for their inhibitory effects on hepatitis C virus (HCV) protease (PR) using in vitro assay methods. Thirty-four extracts showed significant inhibitory activity (>/=60% inhibition at 100 microg/mL). Of these, eight extracts, methanol extracts of Acacia nilotica, Boswellia carterii, Embelia schimperi, Quercus infectoria, Trachyspermum ammi and water extracts of Piper cubeba, Q. infectoria and Syzygium aromaticum, were the most active (>/=90% inhibition at 100 microg/mL). From the E. schimperi extract, two benzoquinones, embelin (I) and 5-O-methylembelin (II), were isolated and found as potent HCV-PR inhibitors with IC(50) values of 21 and 46 microM, respectively. Inhibitory activities of derivatives of I against HCV-PR as well as their effects on other serine proteases were also investigated.

Inhibitory effects of sudanese medicinal plant extracts on hepatitis C virus (HCV) protease.

Haslam’s previous accounts of this area of flavonoid chemistry (Haslam, 1975, 1982a) eloquently summarized the historical developments in the chemistry and biochemistry of this important and complex group of plant phenolics. Also covered were their relationship with condensed tannins and aspects of their characteristic chemical and spectroscopic properties and metabolism.

Flavans and proanthocyanidins

alpha-Glucosidase inhibitory activity was found in aqueous methanol extracts of tochu-cha, dried leaves of Eucommia ulmoides (Eucommiaceae). Five active principles against yeast enzyme were isolated and characterized. Among them, quercetin (1, Ki: 8.5 x 10(-6) M) was considered to contribute mostly to the activity of the tochu leaves. In regard to an animal alpha-glucosidase, rat intestinal sucrase activity was also inhibited by 1.

Mahesh C. Bansal

Papers

Chapter Six – Flavonoid Glycosides

Chapter Three – Flavonoids

Chapter Five – Other Flavonoids

Chapter Four – Isoflavonoids

Chapter Eight - Flavanoids