**5. Kaffir lime fruit (Citrus Hystric DC.)**

Antioxidant production is a control mechanism of the tissue to balance the concentration of ROS. Endogenous antioxidants such as glutathione, pyruvate, and lycopene are produced by the body to deal with the effects of oxidative stress. If the concentration of endogenous antioxidants is insufficient or unbalanced, exogenous antioxidants need the help of exogenous antioxidants. Exogenous antioxidants can be obtained from various sources such as synthetic antioxidants (vitamin E and Vitamin C) and natural antioxidants derived from plants [53].

Kaffir lime (*Citrus hystrix*) is a plant that grows in Indonesia, Malaysia, and Thailand. Citronelal, a monoterpenoid compound that has strong antioxidant activity so that it can be used as an alternative to exogenous antioxidants [54].

Kaffir lime is a fruit that is known to the public as a food source and used as herbal medicine with very high antioxidant activity, so it is widely used in daily needs [55]. Plants of the Citrus genus are known to be rich in polyphenols [56], considered to be one of the antioxidant resources containing sufficient amounts of ascorbic acid/vitamin C, tocopherols, flavonoids, −carotene and other phenolic compounds [57–60]. Polyphenols and flavonoids are good electron donors with their antioxidant power varies from one compound to another [61, 62].
