ABSTRACT
Plant proteins have been investigated for their antioxidant activities, but there are still no reports detailing the antioxidant activity levels of plants in the Zingiberaceae family, which are popular food agents and used in folklore medicine. In this study, the crude rhizome protein extract and associated pepsin/pancreatin protein hydrolysate of 15 plants in the Zingiberaceae family were screened using the DPPH method for antioxidant activity. The protein hydrolysate of C. zedoaria possessed the highest antioxidant activity [IC[50] of 25.7 +/- 6.3 micro g/mL], which was close to that of the reference ascorbic acid [IC[50] of 22.3 +/- 1.8 micro g/mL]. After enrichment by Q Sepharose ion exchange chromatography using a five step elution gradient of increasing NaCl concentration [0, 0.25, 0.5, 0.75 and 1M], the fraction eluting in the 0.5M NaCl [F50] showed the highest antioxidant activity [IC[50] of 41.78 +/- 2.9 micro g/mL], and was found to have weak in vitro cytotoxicity against the HEP-G2 and SW620 cell lines [IC[50] of 200.8 +/- 11.8 and 241.0 +/- 9.3 micro g/mL, respectively], but not the BT474, CHAGO and KATO-3 cell lines. F50 had an estimated molecular weight by MALDI-TOF mass spectrometry of 12,400-12,800 Da