This study examines the antioxidant activity of crude phlorotannins from the brown algae Sargassum hystrix v. buxifolium (Chauvin) J. Agardh, through the inhibition of a lipid peroxidation reaction that is induced by the UV radiation. The antioxidant activity during the UV exposure was investigated using the laser-based photoacoustic method for the detection of the ethylene as indicator for lipid peroxidation. This involves an experiment that isolated crude phlorotannins from the ethyl acetate fraction of the Sargassum hystrix methanol extract, hereafter referred to as PFSH. It results in the antioxidant activity as a potent lipid peroxidation inhibitor. Statistically, such antioxidant activity is not significantly different than the commercial antioxidant, which is vitamin C (p > 0.05). The amount of the total phlorotannins, using the Folin-Ciocalteu method, was measured to be approximately 0.13% w/w. In addition, it is found that PFSH contains phlorotannins with low molecular weight (MW) (<1000 Da). Keywords

The activity of propyl p-benzoyloxybenzoate as a glutathione S-transferase(s) (GSTs) inhibitor has been examined through computational chemistry based theoretical approach and laboratory experiment. This research was related to the nature of GSTs as multifunctional enzymes, which play an important role in the detoxification of electrophilic compounds, the process of inflammation and the effectivities of anticancer compounds. Quantitative Structure-Activity Relationship (QSAR) study, which was established on curcumin and its derivatives using computational chemistry approach, was used to examine the theoretical activity of p-benzoyloxybenzoate as a GSTs inhibitor. Empirical observation on GSTs inhibition was examined using formation reaction model of GS-CNB conjugate through conjugation of 1-chloro-2,4-dinitrobenzene (CDNB) and glutathione (GSH) with GSTs (prepared from rat's liver) as catalysts. The result showed that the difference between the activities of propyl p-benzoyloxybenzoate as a GSTs inhibitor obtained from the computational chemistry approach and the empirical observation were not statistically significant at 95% level of confidence.   Keywords: Propyl p-benzoyloxybenzoate, inhibitor,  glutathione S-transferase (GSTs), QSAR