Antioxidant Activity and Total Phenolics of Some Local Plant Extracts

Author

THEANMALAR MASILAMANI, THAVAMANITHEVI SUBRAMANIAM, SOON WAN ING, LEE PEK YOKE, CHENG HWEE MING & UMA DEVI M. PALANISAMY

Proceeding

The 21st Annual Seminar of the Malaysian Natural Product Society.(Herbal Medicine:Natural Products Society), Palm Garden, Putrajaya Malaysia.

Date

22/11/2005

Keyword

Plant extracts, free radicals, antioxidants, phenolic content, nutraceuticals.

Abstract

Free radicals are any species capable of independent existence that contains one or more unpaired electrons occupying an atomic orbital by itself. They are energetically unstable, highly reactive and short-lived. They cause a chain reaction in the biological membranes and thus lead to various diseases in the body. Antioxidants are substance which significantly delays or prevents oxidation. Lately, a lot of attention has been paid to the role of natural antioxidants especially the phenolic compounds in neutralizing the destructive effect of free radicals. This paper presents the antioxidant screening carried out on some local plant extracts using a variety of free radical scavenging assays and the antioxidant activity of the samples were analyzed by inhibition of autooxidation of linoleic acid. The DPPH and ABTS free radical scavenging assays showed that the aqueous extracts of neem, curry leaves, holy basil, mint, noni and drumstick leaves possessed higher free radical scavenging activities than the ethanolic extracts. The results correlated well with the total phenolics content as they were higher in the aqueous than the ethanolic extracts. It should be noted that the free radical scavenging activity of the aqueous extracts were comparable with the activity of grape seed extract which is a commercial natural antioxidant. The xanthine/XOD assay and inhibition of autooxidation of linoleic acid also showed that the aqueous extract had better activity than the ethanolic extracts. This is comparable with the antioxidant activity of the commercial antioxidant BHT. Thus, it can be concluded that most antioxidants from plants are readily extracted into the aqueous extract. It should also be mentioned that the ABTS assay was seen to be more sensitive than the DPPH assay.