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Ten secondary metabolites were identified from Goniothalamus tapis Miq. The structures of these compounds were elucidated using spectroscopic analyses. It was revealed for the first time that 3-methyl-1H-benz[f]indole-4,9-dione was produced by the organism.

In this study, we examined the effect of N-trans-feruloyltyramine (FA) on melanogenesis in mouse B16 melanoma cells. Melanogenesis was inhibited by FA in a dose-dependent manner. FA exhibited a greater potency than kojic acid as a standard inhibitor of melanogenesis. Moreover, treatment of B16 melanoma cells with FA was found to cause marked decreases in the expression levels of tyrosinase. FA-induced downregulation of tyrosinase resulted in suppression of melanin biosynthesis in murine B16 melanoma cells.

In this research, antioxidant activity, total phenolic, and flavonoid content of n-hexane, ethyl acetate, and methanol fractions of roots, stem bark, and leaves of Elaeocarpus mastersii King were determined by the colorimetric method using DPPH assay (1,1-diphenyl-2-picrylhydrazyl), Folin-Ciocalteu reagent, and aluminum chloride reagent, respectively. Phytochemical screening was evaluated by specific reaction of constituents to the specific reagent. Ethyl acetate fraction had the best value of phenolic content and antioxidant activity among all fractions which the best value was obtained from the leaves (380.99 ± 2.14 mg GAE/g DW and IC50 1.95 ± 0.01 µg/mL) followed by the roots (362.88 ± 1.89 mg GAE/g DW and IC50 2.05 ± 0.01 µg/mL) and the stem bark (341.89 ± 3.97 mg GAE/g DW and IC50 2.36 ± 0.02 µg/mL). All fractions of this plant showed the low value of flavonoid content. The phytochemical screening exhibited that this plant was dominated by phenolic and alkaloid compounds. These results demonstrate the great potential of Elaeocarpus mastersii King as a natural antioxidant and active compounds.

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Syzygium aqueum, consisting of various fruit colors, is one of the plants that have been used as traditional medicine. This study aims to evaluate and compare phytochemical, antioxidant, and cytotoxic activities and total phenolic content of leaves and stem bark extracts of S. aqueum with pink and red fruits, in order to identify the best extract that can be used as a natural antioxidant. Phytochemical constituents were evaluated qualitatively using chemicals, while cytotoxic activities were identified using the brine shrimp lethality test. Total phenolic content was determined via the Folin–Ciocalteu method. Leaves and stem bark of S. aqueum contained flavonoids, phenolics, and triterpenoids, but the stem bark also contained saponins and alkaloids. Methanol and ethyl acetate extracts of leaves and stem bark were categorized as very powerful antioxidants to DPPH (IC50 9.71–38.69 μg/mL) and hydrogen peroxide (IC50 16.44–44.02 μg/mL), while hexane extracts were inactive. Methanol, ethyl acetate, and hexane extracts of leaves and stem bark were categorized as moderately cytotoxic to A. salina larvae (LC50 104.04–440.65 μg/mL). Comparing leaves and stem barks, antioxidant and cytotoxic activities of stem bark extracts were higher than those of leaves extracts. Total phenolic content of leaves extracts was higher than that of stem bark extracts where the order of total phenolic content progressed from methanol extracts > ethyl acetate extracts > hexane extracts. Therefore, the stem bark of S. aqueum was identified as the better source of natural antioxidant compared with the leaves.

Determination of antioxidant content in 14 vegetables has been done using Modified Phenanthroline (MPM), Phenanthroline (PM) and Ferric Reducing Antioxidant Power (FRAP) methods. The SDR values ​​obtained for the MPM and PM methods were (2.65 ± 1.26) % and (3.51 ± 0.88) %, while the recovery values ​​were (100.86 ± 4.45)% and (99.93 ± 3.50) %, respectively. The antioxidant content of vegetables obtained by MPM, PM and FRAP methods were (30.4 ± 1.46 - 515.9 ± 3.32), (25.9 ± 1.13 - 327.3 ± 2.57) and (21.4 ± 0.51 - 371.7 ± 1.10) μmol Fe / g DW, respectively. The antioxidant content obtained with the three methods showed no significant different. The correlation values ​​between MPM - PM, MPM - FRAP, and PM - FRAP methods are 0.9712, 0.9896 and 0.9611, respectively. These values indicate a very strong correlation among the three methods.