Synthesis, characterisation and antitumour activity of some quercetin analogues.

Quercetin is one of the most abundant naturally occurring flavonoid and is associated with a wide range of biological activities, such as antioxidant, antiinflammatory and anticancer activities. However, there are multiple problems associated with the bioavailability of quercetin, thereby restricting its use. Taking this into consideration, the structure of quercetin was modified by removal of multiple hydroxyl groups and introduction of substituents such as Cl, OCH3 and N (CH3)2 on the p-position of the B-ring. The effect of structural modification on the anticancer activity was studied using four different cell lines, including MCF-7, HepG2, HCT-15 and PC-3. Compound 1a has shown an activity better than quercetin in HepG2 cell lines, whereas 1c and 1e showed significant growth inhibition of the HCT-15 cell lines.

A simple HPLC method for quantitation of quercetin in herbal extracts.

A reversed-phase HPLC method with UV detection was developed for the determination of quercetin. The method produced linear response over a wide concentration range, with an average accuracy of 95% and average intra- and interday variation of 0.75 and 0.3, respectively. The exactness of the method was proven by determining the recovery rates from 50 to 150% of standard concentration, which were found within the acceptable range of 95 to 105%. The method was used for quantitation of quercetin in the extracts of Psidium guajava, Vitis vinifera, and extracts rich in quercetin and other flavonols in the flavonoid family.

Antioxidant and antihyperlipidemic activity of Hibiscus sabdariffa Linn. leaves and calyces extracts in rats.

Antioxidant and antihyperlipidemic activities of the extracts of leaves and calyces of Hibiscus sabdariffa were investigated by studying their in vitro inhibitory activity on lipid peroxidation and in vivo effects on cholesterol induced hyperlipidemia. Highest antioxidant activity was exhibited by ethanolic extract of calyces followed by ethanolic extract of leaves followed by aqueous extract of leaves of H. sabdariffa. In cholesterol induced hyperlipidemic model, groups of rats treated with extracts of calyces and leaves of H. sabdariffa showed a significant decrease in the serum TC, LDL-C, VLDL-C, TAG values alongwith an increase in serum HDL-C levels. The treated groups also showed significant decrease in the atherogenic index, LDL-C: HDL-C risk ratios, and in the levels of SGOT, SGPT and ALP activities compared to cholesterol induced hyperlipidemic control group. Significant antihyperlipidemic activity was shown by ethanolic extract of calyces, followed by ethanolic extract of leaves. It was observed from the histopathological findings that rats fed with H. sabdariffa extracts showed decrease in granular degeneration caused by cholesterol feedings. Results suggest that the ethanolic extracts of calyces and leaves of H. sabdarifa containing polyphenols and flavanols possess significant antioxidant and antihyperlipidemic activities.

Antioxidant and Antiinflammatory Activity of Vitex negundo.

Reactive oxygen species are implicated in various inflammatory disorders. Vitex negundo is mentioned in Ayurveda as useful in treating arthritic disorders. The present work was undertaken to evaluate the antioxidant potential and anti-inflammatory activity of the plant. The total methanol extract of the plant was standardized in terms of total polyphenols. The standardized extract in a dose of 100 mg/kg caused a comparable reduction in edema with that of diclofenac sodium (25 mg/kg) when evaluated for antiinflammatory activity by carrageenan-induced rat paw edema method. The extract also exhibited a strong free radical scavenging activity by 1,1-diphenyl-2-picrylhydrazyl method and caused a significant reduction in the formation of thiobarbituric acid reacting substances when evaluated for its lipid peroxidation inhibitory activity. The results strongly suggest that radical quenching may be one of the mechanisms responsible for its antiinflammatory activity.