Isolation and characterization of the compounds responsible for the antimutagenic activity of Combretum microphyllum (Combretaceae) leaf extracts

BACKGROUND

Mutations play a major role in the pathogenesis and development of several chronic degenerative diseases including cancer. It follows, therefore that antimutagenic compound may inhibit the pathological process resulting from exposure to mutagens. Investigation of the antimutagenic potential of traditional medicinal plants and compounds isolated from plant extracts provides one of the tools that can be used to identify compounds with potential cancer chemopreventive properties. The aim of this study was to isolate and characterise the compounds responsible for the antimutagenic activity of Combretum microphyllum.

METHODS

The methanol leaf extract of C. microphyllum was evaluated for antimutagenicity in the Ames/microsome assay using Salmonella typhimurium TA98. TA100 and TA102. Solvent-solvent fractionation was used to partition the extracts and by using bioassay-guided fractionation, three compounds were isolated. The antimutagenic activity of the three compounds were determined in the Ames test using Salmonella typhimurium TA98, TA100 and TA102. The antioxidant activity of the three compounds were determined by the quantitative 2,2-diphenyl-1-picrylhydrazyl (DPPH)-free radical scavenging method. The cytotoxicity was determined in the MTT assay using human hepatocytes.

RESULTS

A bioassay-guided fractionation of the crude extracts for antimutagenic activity led to the isolation of three compounds; n-tetracosanol, eicosanoic acid and arjunolic acid. Arjunolic acid was the most active in all three tested strains with a antimutagenicity of 42 ± 9.6%, 36 ± 1.5% and 44 ± 0.18% in S. typhimurium TA98, TA100 and TA102 respectively at the highest concentration (500 μg/ml) tested, followed by eicosanoic acid and n-tetracosanol. The antioxidant activity of the compounds were determined using the quantitative 2,2 diphenyl-1-picryhydrazyl (DPPH)-free radical scavenging method. Only arjunolic acid had pronounced antioxidant activity (measured as DPPH-free scavenging activity) with an EC₅₀ value of 0.51 μg/ml. The cytotoxicity of the isolated compounds were determined in the MTT assay using human hepatocytes. The compounds had low cytotoxicity at the highest concentration tested with LC₅₀ values >200 μg/ml for n-tetracosanol and eicosanoic acid and 106.39 μg/ml for arjunolic acid.

CONCLUSIONS

Based on findings from this study, compounds in leaf extracts of C. microphyllum protected against 4-NQO and MMC induced mutations as evident in the Ames test. The antimutagenic activity of arjunolic acid may, at least in part, be attributed to its antioxidant activity resulting in the detoxification of reactive oxygen species produced during mutagenesis.

The nonpolar egg wax lipids of the cattle tick, Boophilus microplus (canestrini)

About 40% of the lipids of the egg wax of Boophilus microplus are nonpolar and comprise hydrocarbons (10%) and wax esters (90%). The hydrocarbon fraction is 87% unbranched alkanes, the major components being n-nonadecane (10.8%), n-eicosane (12.1%), and n-heneicosane (9.8%). This fraction also contains 2,4,6-cholestatriene (4.6%). The majority of the acids are branched (77%) the major components being 12-methyl-tetradecanoic (16.3%) and branched hexadecanoic acids (28%). The major alcohols are n26:0 (20.4%), n28:0 (47.3%) and n36:0 (18.2%). A steroid possibly 2,4,6-cholestatrien-25-ol (5.6%), is also present.

The sebaceous glands: twenty-five years of progress

During the last twenty-five years, research on the sebaceous glands has made significant advances. Many of the new findings are related to electron microscopy, quantitative lipid composition studies, and the hormonal and nonhormonal control of sebaceous gland secretion.