Bioactive caffeic acid esters from Glycyrrhiza glabra.

Thin layer chromatography bioautography (using DPPH spray reagent) guided fractionation of Glycyrrhiza glabra led to the isolation of two caffeic acid derivative esters, viz. eicosanyl caffeate (1) and docosyl caffeate (2). The two compounds exhibited potent elastase inhibitory activity, with IC(50) values of 0.99 microg mL(-1) and 1.4 microg mL(-1) for 1 and 2, respectively. The compounds also showed moderate antioxidant activity in DPPH and ABTS scavenging assays. The results indicate a possible role of caffeic acid derivatives, in addition to flavonoids in the anti-ulcer properties of G. glabra.

In vitro interaction of the HIV protease inhibitor ritonavir with herbal constituents: changes in P-gp and CYP3A4 activity.

The purpose of this study was to evaluate in vitro interactions of commercially obtained pure herbal constituents with p-glycoprotein P-gp and cytochrome P-450 3A4 (CYP3A4) activities, which can further modulate the transcellular transport and metabolism kinetics of orally administered drugs. Caco-2 cells grown in the presence of 0.25 micromol/L 1alpha,25-dihydroxy vitamin D3 and multidrug-resistant 1 (MDR1) transfected MDCK cells were used as models to evaluate the effect of purified herbal constituents (quercetin, hypericin, hyperforin from St. John's wort, kaempferol from ginseng, silibinin from milk thistle, and allicin from garlic) on P-gp-mediated efflux of the human immunodeficiency virus (HIV) protease inhibitor ritonavir. In addition, the inhibitory effect of these constituents on CYP3A4-mediated metabolism was determined by using cortisol as a model compound. Silibinin and hyperforin did not significantly alter cellular uptake of H-ritonavir in Caco-2 cells. A similar result was also observed for silibinin when tested in MDR1-MDCK cells. Quercetin, hypericin, and kaempferol exhibited a remarkable inhibition of P-gp-mediated efflux of ritonavir by increasing its cellular uptake in these models. These values were also comparable with the inhibitory effect of quinidine in Caco-2 cells, a well-known inhibitor of P-gp, on ritonavir efflux from Caco-2 cells. Allicin exhibited a concentration-dependent inhibition of ritonavir efflux when tested on MDR1-MDCK cells. There was a significant decrease in the Apical to Basal/Basal to Apical (AP-BL/BL-AP) transport ratio of ritonavir in presence of hypericin, kaempferol, and quercetin. These herbal constituents inhibited the CYP3A4 activity when tested with the Vivid CYP3A4 assay kit, whereas silibinin did not alter cortisol metabolism. Hypericin showed a significant inhibition in reduced nicotinamide adenine dinucleotide phosphate (NADPH)-dependent metabolism of cortisol with 64.6% of intact drug at the end of a 1-hour study. Similarly, kaempferol and quercetin also caused substantial inhibition of cortisol metabolism with 89.7% and 90.1% of intact cortisol, respectively, compared with 45.9% in the control. Prolonged exposure of quercetin resulted in significant increase of mRNA expression of both MDR1 and CYP3A4 levels in Caco-2 cells. However, hyperforin caused upregulation of CYP3A4 and downregulation of MDR1, whereas the effect of silibinin and kaempferol remained inconclusive on these gene expressions. Hypericin, kaempferol, quercetin, and allicin inhibit the efflux and CYP3A4-mediated metabolism of xenobiotics in vitro. Hence, this study warns against the use of herbal constituents along with prescribed HIV protease inhibitors that are substrates for P-gp and/or CYP3A4.

In vivo antiviral efficacy of a dipeptide acyclovir prodrug, val-val-acyclovir, against HSV-1 epithelial and stromal keratitis in the rabbit eye model.

PURPOSE: A dipeptide prodrug of the antiviral nucleoside acyclovir (ACV), val-val-ACV (VVACV), was evaluated in vivo as a potential drug candidate for improving antiviral efficacy against herpetic epithelial and stromal keratitis. METHODS: The effect of 1% VVACV on epithelial keratitis induced by inoculation of HSV-1 strain McKrae (25 microL of 10(5) plaque-forming units [PFU]) in the scarified rabbit cornea and stromal keratitis induced by intrastromal injection of HSV-1 strain RE (10 microL of 10(5) PFU) was compared with that of 1% trifluorothymidine (TFT) and balanced salt solution as the vehicle control. Both eyes of 10 rabbits were used in each treatment group. Lesions were evaluated by slit lamp examinations over a 2-week period after infection. Aqueous humor samples and corneas were analyzed for drug concentrations at the end of each experiment. Cytotoxicity of VVACV in comparison with val-acyclovir (VACV), ACV, and TFT was evaluated in cellular proliferation assays. RESULTS: The dipeptide prodrug VVACV demonstrated excellent activity against HSV-1 in the rabbit epithelial and stromal keratitis models: 1% VVACV was as effective as 1% TFT. The prodrug was also less cytotoxic than TFT, which is the only effective drug currently licensed and routinely used for topical treatment of ocular herpes infections in the United States. CONCLUSIONS: The less cytotoxic and highly water-soluble prodrug VVACV, which showed excellent in vivo activity against HSV-1 in rabbit epithelial and stromal keratitis, is a promising drug candidate for treatment of ocular HSV infections.