Purpose: To evaluate the antibacterial and cytotoxic activities of the secondary metabolites of
Lobophytum
sp.
Methods: Maceration with methanol: chloroform (1:1) was applied to extract the coral material.
Chromatographic and spectroscopic techniques were employed for fractionation, isolation and
elucidation of pure compounds. Antibacterial activities were performed by well diffusion method against
three Gram-positive and four Gram-negative bacteria. Brine shrimp lethality test was employed to
predict toxicity, while antitumor activity were tested by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-
diphenyltetrazolium bromide (MTT) method against Ehrlich carcinoma cells.
Results: Four sesquiterpenes, one cembranoid type diterpenes and two steroids were isolated.
1
exhibited significant antibacterial activity against four tested bacteria ( P.
aeruginosa
, S.
aureus
, S.
epidermis
, and S.
pneumonia
) with MIC value of 15 μg/mL. Moreover,
1 showed high diameter zone of
inhibition ranging from 16 - 18 mm against test bacteria. Compounds
4 and
5 displayed moderate
antibacterial activity against all test bacteria with inhibition zone diameter (IZD) ranging from 11 – 15
mm and MIC values of 30 μg/mL.
2,
3,
6 and
7 exhibited weak antibacterial activity (IZD, 7 - 11 mm;
MIC ≥ 30 μg/mL). In addition, only diterpene compound (4) showed high toxicity against A. Salina and
antitumor activity against Erhlich carcinoma cells with the LD
50 of 25 and 50 μg/mL, respectively.
Conclusion: This study reveals the strong antibacterial activity of sesquiterpene alismol (
1) and the
potential antibacterial and antitumor activity of cembranoid type diterpene, cembrene A (
4).
