The genetic polymorphism of CYP2C19 was examined in three Southeast Asian populations. This study was conducted in 774 Thais, 127 Burmeses and 131 Karens. Genomic DNA was extracted from leucocytes and analyzed by the PCR-RFLP technique. Genotype analysis revealed that the allele frequencies of CYP2C19*1, CYP2C19*2 and CYP2C19*3 in the Thais were 0.68, 0.29 and 0.03, respectively, and those of the Burmese population were 0.66, 0.30 and 0.04, respectively. For Karens, the minority ethnic in Mynmar, the allele frequencies of CYP2C19*1, CYP2C19*2 and CYP2C19*3 were 0.71, 0.28 and 0.01, respectively. The prevalence of PM estimated from genotype data among these three ethnic populations were 9.2%, 11.0%, and 8.4%, respectively. The PM phenotype and the frequencies of CYP2C19 defective alleles, particularly CYP2C19*3 among these three Southeast Asian ethnics appeared to be lower than other Asian populations. Lower prevalence of CYP2C19 PM suggests that these ethnics may have different capacity to metabolize drugs that are substrates of CYP2C19. Certain drug dosage regiments should be considered differently for Asian populations.

Ethyl caffeate (EC), octyl caffeate(OC), benzyl caffeate(BC) and phenethyl caffeate(PC) were synthesized and evaluated for scavenging of superoxide anion, nitric oxide radical and 1,1-diphenyl-1-picrylhydrazyl radical (DPPH). Antioxidant activity was investigated with reducing power method. Pooled human liver microsome was used for investigating the effects on cytochrome P450 1A2 (CYP1A2) catalytic activities by using phenacetin as a substrate. Dixon and Cornish-Bowden plots were used for enzyme kinetic analysis. The EC, OC, BC and PC potentially inhibited superoxide anion, nitric oxide and DPPH radicals. IC(50) values of superoxide anion scavenging of EC, OC, BC and PC were 16.42, 79.83, 123.69 and 123.69 µg/ml, respectively. EC was more potent than OC and BC in terms of nitric oxide radical scavenger: IC(50) values of EC, OC and BC were 24.16, 37.34 and 52.64 µg/ml, respectively. In addition, the IC(50) values of EC, OC, BC and PC on DPPH radical scavenging were 70.00, 184.56, 285.34 and 866.54 µg/ ml, respectively. The IC(50) values of EC, OC, BC and PC on phenacetin O-deethylation were 124.98, 111.86, 156.68 and 31.05 µg/ml, respectively. Enzyme kinetics showed that the type of inhibition mechanism was mixed-type. The result of this study shows that caffeic acid ester analogues potentially scavenge free radicals and inhibit catalytic activity of CYP1A2. This may lead to important implications in the prevention of CYP1A2-mediated chemical carcinogenesis.

Background. Cissus quadrangularis Linn. (CQ) is a medicinal plant with good evidence for the treatment of hemorrhoids, listed in the Thai National List of Herbal Products in the oral dosage form. Acmella paniculata (Wall ex. DC.) R. K. Jansen. (AP) is a medicinal plant with a local anesthetic effect. Objective. To investigate the potential of rectal suppositories containing CQ and AP extracts to alleviate symptoms of hemorrhoids compared with the commercialized rectal suppository containing hydrocortisone and cinchocaine. Materials and Methods. Hemorrhoid outpatients (n = 105) with different severity grades (I, II, or III) from eight hospitals in northern Thailand were included in this study. Hemorrhoid severity was graded by proctoscopy associated with either anal pain or bleeding related to hemorrhoids or both. The patients were randomly allocated to two groups: CQ-AP group (n = 52) or the commercialized rectal suppository group (n = 53). One suppository was rectally administered twice daily in the morning and at bedtime for seven days. Evaluations were performed by physicians on days 1, 4, and 8 of the study. The primary endpoints were bleeding and prolapse size, while the secondary endpoint was anal pain. Results. Baseline demographics, lifestyle, constipation, number of prolapses, grade of hemorrhoid severity, and duration of experiencing hemorrhoids were comparable in both groups of patients. The effects of CQ-AP and the commercialized rectal suppository on bleeding, prolapse size, and anal pain were comparable. The patients in both groups were satisfied with both products at comparable levels and stated a preference for further use in the case of hemorrhoids recurrence. In terms of safety, the patients in the commercialized rectal suppository group experienced a higher incidence of adverse events, including anal pain and bleeding. Conclusion. Rectal suppositories containing a combined extract of CQ and AP show potential in alleviating hemorrhoidal symptoms with a good safety profile.

From our results, caffeic acid and its amide analogues are in vitro inhibitors of human CYP1A2 catalytic activity and free radical formation. They may be useful to be developed as potential chemopreventive agents that block CYP1A2-mediated chemical carcinogenesis.