QUN YU^1,2, CHUAN LI²*, ZHEN-HUA DUAN¹*, XIAO-XI ZHANG², BING LIU²
*Corresponding author
1. Institute of Food Research, Hezhou University, Hezhou, China  
2. College of Food Science and Technology,Hainan University, Haikou, China

Abstract

The aim of this study was to evaluate antioxidant and antimicrobial activities of different extracts from Clinacanthus nutans. Powdered leaf samples were extracted with 70% ethanol and distilled water using ultrasonic-assisted extraction method, respectively. The strongest antioxidant activities in 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging, ·OH scavenging and reducing power were obtained from ethanol extracts compared to distilled water. Ethanol extracts also possessed the highest antimicrobial activity against Staphylococcus aureus among three selected microorganisms, with an inhibition zone diameter of 12.5 ± 0.7 mm at 10 mg/mL. Furthermore, pH at 5-6 and temperature at 40-60 °C conditions were good for antimicrobial activity. These results illuminated a potential market role for Clinacanthus nutans as a functional food ingredient or nutraceutical.

INTRODUCTION

Clinacanthus nutans (Family: Acantaceae) is known as Sabah Snake Grass or Belalai Gajah in Malaysia (1). Recently, it has received much attention by numerous researchers because of its therapeutic characteristics. The medicinal plant is the one of sources to reduce cancer, increase the immune system and reduce inflammation (2, 3). In Indonesia and Thailand, it’s an important traditional herbal medicine because of the treatment of skin rashes, fever and diabetes mellitus (4, 5). Due to the resistance of bacterial microorganisms, recently many scientists and researchers have drawn attention to the extracts of Clinacanthus nutans (6). However, little information is known about the antioxidant and antimicrobial activities of Clinacanthus nutans. 

Studies have shown that many bioactive substances act as exogenous antioxidants, neutralizing free radicals, reducing oxidative stress and support the antioxidant system, such as polyphenols, flavonoids and other antioxidant compounds (7,8). It was needed to investigate the free radical-scavenging and antimicrobial activities of the plant-based extracts. Antioxidant activities of h ...