In vitro antioxidant activities of several local herbs / Sarah Diyana Shafie

Antioxidants play an important role in inhibiting lipid peroxidation and scavenging radicals, thus providing protection to humans against infections and degenerative diseases. The literature showed that the antioxidant capacity of herbs and vegetables are high (Rahmat et al. 2003). This study was thus carried out to determine the in vitro antioxidant capacity of a Malaysian herb. Nineteen types of herbs that are commonly consumed by Malaysian people were screened for antioxidant activity measured by photochemiluminescence. This method tests the ability of the herbs to scavenge free radicals. Among the screened herbs, the most potent radical scavenging activities was found in Eugenia polyantha (daun salam). Diplazium esculentum (pucuk paku) had the second highest antioxidant activity. From these results, Diplazium esculentum (pucuk paku) was selected for further study in an in vitro lipid peroxidation assay. Daun salam was not selected for the above mentioned assay as it was difficult to obtain the herb in large enough amounts. In the in vitro lipid peroxidation assay, tert-butylhydroperoxide (t-BOOH) was used to induce lipid peroxidation in rat liver microsomes. The t-BOOH induced lipid peroxidation assay system was first optimized, before it was used to test the antioxidant activities of the Diplazium esculentum extract. Lipid peroxidation was monitored by the thiobrbituric reactive substance (TBARS) method. The optimum microsomal protein concentration for use in the lipid peroxidation assay was found to be 0.2 mg/ml while the optimum period for incubating the microsomes with t-BOOH was 30 minutes. The ability of Diplazium esculentum extract to inhibit microsomal lipid peroxidation induced with t-BOOH was then measured. Trolox was used as a positive control. Both Diplazium esculentum extract and Trolox were capable of reducing the TBARS levels with IC50 values of 4.10 + 0.06 pg/ml for Trolox and 5.62 + 0.06 pg/ml for the Diplazium esculentum extract. The IC50 value of Diplazium esculentum extract was comparable to that of Trolox. Overall, the results obtained suggested that the extract possessed an in vitro antioxidant activity through radical scavenging ability and inhibition of lipid peroxidation. The antioxidant activity of extract was comparable to Trolox, a fact that should encourage more in vitro studies and future in vivo work.