Sesamol: an efficient antioxidant with potential therapeutic benefits.

Sesamol has been shown earlier to exhibit antimutagenic (reactive oxygen mediated) and antiageing activity in our lab and it has also been found to exert chemopreventive effect. Here we report the in vitro antioxidant activity of sesamol. As most of the antioxidants act due to their property to auto-oxidise and the pro- or antioxidant activity would depend on the concentration of the agent used and the free radical source, at least 6 dilutions in concentration range of 5-1000 nmoles of sesamol were selected for each test system. Further the antioxidant activity was compared with a water soluble antioxidant (ascorbic acid). Eventhough some preliminary studies on the antioxidant activity of sesamol have been reported in DPPH assay & inhibition of lipid peroxidation, it is not complete. We, here in report comprehensively (both in terms of the no. of doses and also a variety of test systems being employed) on the antioxidant activity of sesamol. Furthermore, since all the data has been generated by the same workers and under same laboratory conditions, hence is scientifically significant. Also the process of dose selection as discussed earlier is more scientific; and the data treatment, i.e. calculation of IC(50) values and comparisons with ascorbic acid has been statistically validated. In conclusion, sesamol was found to be an efficient scavenger of the entire range of ROS in several test systems pointing towards the potential of sesamol to be developed as a possible therapeutic.

Ginseng extract exhibits antimutagenic activity against induced mutagenesis in various strains of Salmonella typhimurium.

Ginseng has been reported to exhibit antioxidant and antimutagenic activity. The present study was undertaken with a view to confirm whether the antioxidant activity of Ginseng is responsible for its antimutagenic action. The concentrated root extract of Panax ginseng (Ginseng extract I) and its lyophilized powder (Ginseng extract II) obtained from two different manufacturing houses, were tested against mutagenesis using the well-standardized Ames microsomal test system. The extracts exhibited antimutagenic effect against hydrogen peroxide induced mutagenesis in TA100 strain, and against mutagenesis produced by 4-nitroquinoline-N-oxide in both TA98 and TA100 strains of Salmonella typhimurium. Both the extracts failed to show any antimutagenic potential against tert-butyl hydroperoxide (an oxidative mutagen) in TA102 strain, a strain highly sensitive to active oxygen species. The extracts also indicated a weak antioxidant activity in a series of in vitro test systems viz., 1,1-diphenyl picryl hydrazyl (DPPH) assay, hydrogen peroxide scavenging and superoxide anion scavenging. The results indicate that the protective effects shown by ginseng extract(s) against 4-nitroquinoline-n-oxide and hydrogen peroxide induced mutagenesis in TA98 and TA100 could mainly be due to its property to initiate and promote DNA repair rather than free radical scavenging action.

Screening methods for antioxidants-a review.

Various environmental, physical and chemical stresses on cells may induce either an overproduction of ROS (Reactive Oxygen Species) or a deficiency of antioxidant enzymes. ROS are responsible for various cellular anomalies like protein damage, deactivation of enzymes, alteration of DNA and lipid peroxidation which in turn leads to pathological conditions like carcinogenesis, reperfusion injury, rheumatoid arthritis, diabetes etc. The regular intake of antioxidants seems to limit or prevent the dangerous effects caused by ROS. Thus, to maintain cellular health, it is important to have a specific and effective antioxidant that scavenges multiple types of free radicals so that it can be used in multiple diseases. Different in vitro and in vivo test systems are available in the literature to assess the free radical scavenging activity of various compounds. Based on the efficiency of free radical scavenging, the compounds are classified into strong, moderate and weak antioxidants. The following review explains the brief procedure and the principle behind various methods available in the literature, which can be used to determine the scavenging of different types of free radicals.

Antimutagenic and antioxidant/prooxidant activity of quercetin.

The present study has been performed to evaluate the antimutagenic activity of quercetin, ascorbic acid and their combination against an oxidative mutagen. An effort was also made to correlate this activity to the in vitro antioxidant activity of these agents. Antimutagenicity testing was done in Ames Salmonella Assay system using Salmonella typhimurium TA102 against t-butylhydroperoxide as an oxidative mutagen. In vitro antioxidant scavenging activity was tested for DPPH free radical, superoxide anion, hydrogen peroxide and hydroxyl radical in their specific test systems. Quercetin (0.5-8 nmole/plate) and ascorbic acid (0.1-100 micromole/plate) showed significant effect. Quercetin (4 and 8 nmole/plate) when combined with ascorbic acid (500 nmole/plate) showed an increase in the antimutagenic activity. In vitro antioxidant activity of quercetin was better than ascorbic acid in all the test systems used. The study indicated that the antimutagenic activity of quercetin was not solely accountable by its antioxidant nature. However, in vitro free radical scavenging activity of quercetin correlated well with the antimutagenic activity.

Interference of isonicotinyl hydrazone in the microbiological analysis of rifampicin from anti-tuberculosis FDC products containing isoniazid.

Microbiological assay is a sensitive method for the estimation of rifampicin (R). In the present study, interference due to isonicotinyl hydrazone (HYD), an interaction product of R and isoniazid (H), was checked during microbiological analysis of R, employing Bacillus subtilis and Sarcina lutea. The assays were done by disc diffusion method. Both R and HYD showed linear log response curves in the range of 0.01-10microg. In the presence of HYD, R was overestimated when tested against S. lutea and underestimated in case of B. subtilis. The same extent and type of interference was observed on assay of a marketed anti-tuberculosis fixed-dose combination product, subjected to accelerated stability testing (40 degrees C/75% RH) for 1 month. This means that response of organisms used in microbiological assay of R might vary in the presence of HYD, with possibility of incorrect conclusions. Therefore, the study suggests that before a microbiological method involving a particular organism is extended to the determination of R in FDC formulations containing H, it should be tested for the influence of HYD and used only if non-interfering.

Delineation of antimutagenic activity of catechin, epicatechin and green tea extract.

Tea is consumed worldwide as second largest to water in popularity as a beverage. It has been reported that tea extracts have antibacterial, antiviral, antioxidative, antitumor and antimutagenic activities. The protective effect of green tea has been assumed to be due to the powerful scavenging and antioxidative property of high concentrations of unpolymerised catechins and their gallates. In the present proposal green tea extract (GT), (+)-catechin (C) and (-)-epicatechin (EC) were investigated for their antioxidant activity by different in vitro methods like (i) DPPH assay (ii) superoxide anion scavenging and (iii) hydrogen peroxide scavenging activity. Further these agents were also tested against mutagenesis using the well-standardized Ames microsomal test system. The Ames tester strain Salmonella typhimurium TA102, which readily responds to reactive oxygen species, was used and the antimutagenic activity was evaluated against oxidative mutagens tertiary butyl hydroperoxide (ID50-24.41, 29.63 and 113.23 microg for EC, C and GT, respectively) and hydrogen peroxide (ID50-17.3, 18.4 and 88.1 microg for EC, C and GT, respectively). Ascorbic acid was used as a standard antioxidant in all the experiments. Results indicate that all the three agents possess excellent DPPH free radical scavenging activity (IC50-1.5 microg for EC, 3.45 microg for C and 3.8 microg for GT), good hydrogen peroxide (IC50-11.18 microg for EC, 13.5 microg for C and 11.78 microg for GT) and superoxide anion scavenging (IC50-1.64 microg for EC, 1.74 microg for C and 3.52 microg for GT) activities. Further, they also show antimutagenic activity in the above-mentioned test systems establishing their antioxidant nature to be responsible for such activity. The in vitro antioxidant activity correlates well with the antimutagenic action. (-)-Epicatechin is indicated to be a better agent in comparison to the other two agents (ID50-1.2 times more than C and 5 times more than GT in antimutagenicity studies against t-BOOH and hydrogen peroxide induced mutagenesis). Ascorbic acid however showed a much less activity (ID50-12.1 mg against t-BOOH and 7.2 mg with hydrogen peroxide induced mutagenesis).