Antioxidant Activities and Polyphenolic Constituents of Bitter Bean Parkia Speciosa

Abstract

Bitter bean (Parkia speciosa), also known as petai, is a popular non-timber forest product. Traditionally, its fruits are consumed as vegetables and herbal medicines in Malaysia. The present study aimed to evaluate the antioxidant activities of aqueous and ethanol extracts of P. speciosa empty pods using various antioxidant assays, as well as examining their polyphenolic constituent contents. Results showed that with the exception of superoxide radical scavenging activity, ethanol extracts possessed stronger DPPH and ABTS radical scavenging, anti-lipid peroxidation, metal chelating and reducing power activities than aqueous extracts. It was found to contain a higher level of total flavonoids and total phenols than aqueous extracts. The major polyphenolic constituents present in these extracts were gallic acid, catechin, ellagic acid, and quercetin. Although aqueous extracts contained a higher level in gallic acid, its catechin, ellagic acid, and quercetin contents were lower than ethanol extracts. Taken together, the higher amount of polyphenolic compounds present in ethanol extracts could have contributed to its stronger antioxidant activities than aqueous extracts; these results also provided the chemical basis for certain health benefits claimed of P. speciosa empty pods in folk medicine and as foods.

Keywords:

• Parkia speciosa
• Bitter bean
• Antioxidant activity
• Flavonoids
• Phenols