Rahmawati AN, Astirin OP, Pangastuti A. 2018. Intracellular antioxidant activity of Muntingia calabura leaves methanolic
extract. Nusantara Bioscience 19: 210-214. Excessive reactive oxygen species (ROS) results in oxidative damage that destroys proteins,
lipids, and DNA, resulting in various diseases and accelerating the aging process. Antioxidants are compounds that have the ability to
suppress oxidative stress. Muntingia calabura has a high phytochemical content, especially the phenolic group that can act as
antioxidant. This study aimed to determine the intracellular antioxidant activity of M. calabura leaves methanolic extract (MLME)
through intracellular ROS levels in 3T3 fibroblast cells under normal condition and oxidative stress due to UVB exposure. Tests were
performed using the DPPH (Diphenyl-1-picrylhydrazyl) method and modified NBT (Nitroblue Tetrazolium). Testing of antioxidant
activity with DPPH method obtained result that MLME had high antioxidant activity with IC50 value of 3.030 μg mL-1, while
intracellular antioxidant activity with modified NBT method showed that MLME statistically had significant effect on intracellular ROS
level under normal condition (p < 0.05) based on dose-dependent manner, but not significant (p > 0.05) under oxidative stress condition.
Significant effects were only shown at a concentration of 20 μg mL-1 against the control of oxidative stress due to UVB exposure.