Antioxidant Capacity of Fresh and Dry Leaf Extracts of Sixteen Scutellaria Species

Abstract

The antioxidant capacity of 16 Scutellaria species was examined using Trolox equivalent antioxidant capacity (TEAC) assay. Total polyphenol, antioxidant capacity estimation and flavonoid content measurements were conducted on fresh and air dried leaf extracts. The highest total polyphenol content was obtained in dry leaf extracts of S. ocmulgee at 732.41 67 mg/g of gallic acid equivalent. Dry leaf extracts of S. ocmulgee registered 2480.93 μmol/g of Trolox equivalent antioxidant capacity and the highest total flavonoid content with 200.63 μg/mL from fresh leaf extracts of S. alpina. Rosemary (Rosmarinus officinalis), a common herb with known high antioxidant potential, was used as a standard for comparison with the Scutellaria species. INTRODUCTION The genus Scutellaria, commonly known as skullcap (scullcap) belongs to the family Lamiaceae (Mint family). Of the 400 known Scutellaria species, over 90 of these plants have been recorded as growing in North America. In the current study, 20 Scutellaria spp. that grow in and adjacent to the state of Georgia were used (Joshee et al., 2002). Scutellaria ocmulgee and Scutellaria montana, two species that grow in Georgia, are relatively rare and protected by the state and federal government (Chafin, 2007). Scutellaria species are known for their potential pharmaceutical/therapeutic properties and have been used in the traditional medicine of many countries for their anti-inflammatory, antioxidant, and anti-viral properties useful in treating human ailments (Huang et al., 2005b; Shang et al., 2010). S. baicalensis, native to China, and S. barbata, from Korea, have been extensively employed in traditional Chinese medicine (TCM) and in Japanese Kampo medicine (JKM) (Watanabe et al., 2002; Murch et al., 2004). Leaf extract from S. ocmulgee has demonstrated inhibitory properties against malignant gliomas (Parajuli et al., 2009, 2011). Plants, such as basil (Ocimum spp.), mint (Mentha spp.), rosemary (Rosmarinus officinalis), lavender (Lavandula spp.), and Baikal skullcap (Scutellaria baicalensis), are known to contain relatively high levels of phenolics and have demonstrated antioxidant activity (Zheng and Wang, 2001; Shao et al., 2004; Waisundara, 2010; Atanassova and Georgieva, 2010). Leaves from peppermint (M. x piperita), rosemary, sage (Salvia spp., spearmint (M. spicata), and thyme (Thymus spp. growing in a greenhouse exhibit total polyphenol (TPP) and Trolox equivalent antioxidant capacity (TEAC) as plants grown under field conditions, plus anti-tumorigenic activity against colon cancer cells (Yi and Wetzstein, 2010; 2011). Free radicals can cause disorders, such as atherosclerosis, central nervous system injury, and gastritis in the human body (Kumpulainen and Salonen, 1999; Pourmorad et al., 2006). By boosting the human immune system, plant-based antioxidants block free radicals produced through oxidation (Schuler, 1990), thus inhibiting chain reactions that could lead to degradation and death of cells (Pratt, 1992; Velioglu et al., 1998; Hu and Willett, 2002). The antioxidant activity delays and inhibits oxidation of cellular components and molecules (Nijveldt et al., 2001). Thus, the level of activity of various phytochemicals is important for the evaluation of their potential health benefit to humans. Vaidya et al.: Antioxidant Capacity of Fresh and Dry Leaf Extracts of Sixteen Sc