Abstract

• Cinchona succirubra Pav. (Kwi-neing in Myanmar) has been used in traditional medicine due to the presence of alkaloids such as quinine, quinidine, cinchonine and cinchonidine. The alkaloids contained in cinchona bark are powerful drugs and so C. succirubra has remarkable biological activities. The present study focuses on screening of some bioactive constituents from the bark of C. succirubra Pav. (Kwi-Neing). Preliminary phytochemical investigation was carried out by the reported chemical methods. The extractable matters of the bark of C. succirubra were prepared by extracting powdered sample with polar solvents such as ethanol and water using WHO standard method. Some organic constituents, compound 1 (terpenoid), compound 2 (phenolic compound) and compound 3 (alkaloid) were isolated from EtOH crude extract by column chromatographic separation technique. The isolated compounds were identified by treating with specified reagent on TLC and by UV and FT IR spectroscopic methods. The antimicrobial activity of crude extracts and isolated compounds 2 and 3 was determined by agar well diffusion method against six species of microorganisms namely Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus pumilus, Candida albicans and E.coli. Both extracts showed the pronounced antimicrobial activity against Bacillus subtilis (inhibition zone diameter = 30 mm). In addition, compound 3 showed the strong antimicrobial activity against E.coli (inhibition zone diameter = 33 mm). Antioxidant activity of crude extracts and compounds 2 and 3 was also screened by Dot-Blot and DPPH staining method. It was found that the violet colour of DPPH disappeared from 400 µg up to minimum concentration of 100 µg for EtOH extract and 200 µg for H2O extract. In addition, compound 2 showed potent antioxidant activity with sample concentration 25 µg (31.25 µg/mL). The mineral contents of bark of C. succirubra were quantitatively determined by AAS method. Calcium (Ca) was found to be the principal element.