Antioxidative activity and total phenolic compounds of root, leaf and petiole of four accessions of Centella asiatica (L.) Urban, namely CA 01, CA 05, CA 08 and CA 11, were evaluated. Antioxidative activity of the extracts was measured using the ferric thiocyanate (FTC) method and thiobarbituric acid (TBA) test. The antioxidative activities were then compared with that of α-tocopherol (natural antioxidant) and butylated hydroxytoulene or BHT (synthetic antioxidant). The results showed that CA 01 and CA 05 had the highest antioxidative activities among the accessions tested. Results also showed that both leaf and root of C. asiatica had high antioxidative activity, which was as good as that of α-tocopherol. The total phenolic content, determined according to the Folin-Ciocalteu method, varied from 3.23 to 11.7 g/100 g dry sample, and showed strong association (r2=0.90) with antioxidative activity. The results suggest that phenolic compounds are the major contributors to the antioxidative activities of C. asiatica.

No abstract

Analyses on biological activities of Gnetum gnemon were done to determine the total phenolic and antioxidants of the plant. Four parts of G. gnemon were used in this study, which were leaf, bark, twig, and seeds of the plant. All parts were extracted in methanol, ethanol, hexane, chloroform and hot water using reflux. The total phenolic content of the plant extracts were determined by using Folin-Ciocalteu method. The results demonstrated that the bark from hot water extract showed the highest total phenolic at 10.71±0.01 mg GAE/ FDW, while the lowest was chloroform extract of seed at 2.15±0.01 mg GAE/ FDW. The antioxidant activity of the plant extracts were determined by using DPPH and FRAP assays, respectively. The DPPH results showed that all plant extracts demonstrated weak free radical scavenging activity tested at the final concentration of 300 μg/ml. In contrast, the methanolic twig extract showed strong reducing power activity (FRAP) at 83.55±1.05%, while the hot water seed extract showed the least activity at 41.86±4.22% tested at the final concentration of 300 μg/ml. However, there were no correlation between total phenolics and both antioxidant assays tested.

A new carbazole alkaloid, 3-carbomethoxy-2-hydroxy-7-methoxycarbazole, Clausine-TY (1), together with two known carbazole alkaloid, Clausine-H (2) and Clausine-B (3), were isolated from the ethyl acetate extract of the stem bark of the Malaysian Clausena excavata. The structures of these compounds were elucidated by spectroscopic analyses. The new carbazole alkaloid shows significant cytotoxicity against CEM-SS cell line.

Our recent studies on the stem bark of Calophyllum mucigerum (Guttiferae) have yielded a new coumarin mucigerin, a prenylated xanthone cudraxanthone C and the common steroidal triterpenes friedelin and stigmasterol. Structural elucidations of these compounds were achieved using 1H NMR, 13C NMR, DEPT, COSY, HETCOR and HMBC experiments while MS gave the molecular masses. Cytotoxic assays using CEM-SS cell line (T-lymphoblastic leukemia) on the crude extracts of the stem bark indicated some activity. The crude extracts were also found to be moderately toxic against the larvae of Aedes aegypti. This article reports the isolation and identification of mucigerin as well as bioassay data.