Curcuma caesia (black turmeric), a member of the Zingiberaceae family, is a perennial herb with bluish-black rhizome. In this study, antioxidant potential of sequential extracts of fresh and dried rhizomes was analyzed by DPPH radical scavenging assay, total antioxidant capacity, ferric reducing activity and TBARS assay. Total phenol content was estimated by the Folin-Ciocalteau method. C. caesia showed significant antioxidant activity in chloroform, benzene and ethyl acetate extracts. The chloroform extract was highly effective as free radical scavengers, electron-donating agents and reducing molybdate ions except for reducing lipid peroxidation. The highest total phenol content was also exhibited by chloroform and benzene extracts. Antioxidant potential expressed by C. caesia in the sequential extracts could be effectively utilized for identification of the bioactive compounds for future phytopharmacological applications.
Key words: Curcuma caesia, antioxidants, reactive oxygen species, total phenols
Free radicals, which are molecules with unpaired electrons, play a key role in the development of various degenerative diseases, including aging, cancer, inflammation, diabetes, Alzheimer’s disease and other neurodegenerative disorders[1,2]. They are formed as intermediates of various biochemical reactions, but when generated in excess can result in oxidative damage to DNA, proteins and lipids. Free radicals containing oxygen, known as reactive oxygen species (ROS), are the most biologically significant free radicals. ROS include the superoxide and hydroxyl radical, plus derivatives of oxygen that do not contain unpaired electrons, such as hydrogen peroxide, singlet oxygen, and hypochlorous acid.
A class of compounds known as antioxidants control the formation of free radicals, by blocking the process of oxidation via scavenging these free radicals. Antioxidants are compounds that inhibit or delay oxidation of other molecules by terminating the initiation or propagation of oxidizing chain reactions. Restriction on the use of synthetic antioxidants due to their carcinogenic nature[4,5] has led to a growing interest in recent years in natural antioxidants of plant origin with low cytotoxicity for application in food industry to combat food deterioration. Natural antioxidants present in foods have attracted interest because of their safety and potential nutritional and therapeutic effects. It is recognized that besides a role in endogenous defence of plants, human consumption of dietary antioxidants affords protection against some pathological events.
In recent years, synthetic antioxidants used as preservatives in processed foods, such as butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are reported to be detrimental to human health and the search for plant-derived substances has intensified[7-9]. Thus, attention is now increasingly paid to the development and utilization of more effective and non-toxic antioxidants, of...