Comparative study of aqueous and ethanolic aromatic malaysian herbs extracts using four antioxidant activity assays

Abstract

Recently, much attention on medicinal herbs research has been focused on those herbs that are used for the prevention of various diseases. Herbs in addition to contributing taste and aroma to foods also contain a variety of bioactive substances which are responsible for their biological activities. In this study, Total Phenolic Content (TPC), Total Flavonoid Content (TFC) and antioxidant activities of aromatic Malaysian herbs namely Persicaria hydropiper (L.) H. Gross, Citrus hystrix DC, Murraya koenigii Spreng., Etlingera elatior (Jack) R.M. Sm., Cymbopogon citratus Stapf. and Kaempferia galanga L., using water and ethanol as extraction solvents were determined. The antioxidant activities of these herbal extracts were determined by using four different assays, DPPH radical scavenging activity, Ferric Reducing Antioxidant Power (FRAP), P-carotene bleaching and Oxygen Radical Absorbance Capacity (ORAC) assays. Both extracts of P. hydropiper showed the highest TPC, TFC and reducing power in FRAP assay. In DPPH radical scavenging activity assay, the lowest EC50 values were shown by both extracts of P. hydropiper and M. koenigii and these two herbs showed no significant difference (p>0.05) with standards ascorbic acid and BHA/BHT combination. Among aqueous extracts, P. hydropiper and M. koenigii had the highest% inhibition in P-carotene bleaching assay and showed no significant difference (p>0.05) with BHA/BHT combination. However, among ethanolic extracts, M. koenigii had the highest% inhibition but all of the ethanolic extracts had lower percentage inhibition than BHA/BHT combination. In ORAC assay, aqueous P. hydropiper, C. hystrix and M. koenigii extracts showed significantly higher values (p<0.05) compared to other sample extracts, however, no significant difference (p>0.05) were observed among ethanolic extracts. For both aqueous and ethanolic extracts, there were strong correlation between TPC and TFC with DPPH radical scavenging activity, FRAP and P-carotene bleaching assays. The results provided evidence that the aromatic Malaysian herbs studied could be a potent source of natural antioxidants and can be used as functional food ingredients. © 2013 Academic Journals Inc.