Chemical composition and antioxidant activities of essential oil and oleoresins from Curcuma zedoaria rhizomes, part-74
Introduction
It has been established that oxidative stress is among the major causative factors in the induction of many chronic and degenerative diseases including atherosclerosis, heart disease, cancer, ageing, diabetes mellitus and others (Young & Woodside, 2001). The most effective way to eliminate free radicals which cause the oxidative stress is with the help of antioxidants. Currently, there is a growing interest toward natural antioxidants of herbal resources (Velioglu, Mazza, Gao, & Oomah, 1998). Epidemiological and in-vitro studies on spices, medicinal plants and vegetables strongly supported this idea that plant constituents with antioxidant activity of exerting protective effects against oxidative stress in biological system. C. zedoaria (Berg.) rosc, (Zingiberaceae) has long been used as folk medicine.
Curcuma (Zingiberaceae) is a large genus of rhizomatous herbs distributed in tropical and subtropical regions especially in India, Thailand, Malay Archipelago, IndoChina, and Northern Australia. Many phytochemical studies on the extracts and essential oils of several Curcuma species, especially C. longa, have identified curcuminoids and sesquiterpenoids as the major components (Itokawa, Shi, Akiyama, Morris-Natschke, & Lee, 2008), and these compounds have been identified as the major groups of antioxidants in the plants. The antioxidant activity of Curcuma longa, has been measured by various chemical methods such as DPPH radical scavenging activity assay, superoxide anion radical scavenging activity assay, ferric reducing/antioxidant power (FRAP) assay, and metal chelating activity assay (Zhao et al., 2010, Himaja et al., 2010).
The objectives of the present study were to investigate the antioxidant activity of the essential oil and oleoresins of C. zedoaria, compared to synthetic antioxidants carrying out in-vitro tests including determination of peroxide, thiobarbituric acid values; scavenging effects on 1,1′diphenyl-2-picrylhydrazyl (DPPH); reducing power and total antioxidant activity by ferric thiocyanate (FTC) methods. The chemistry of volatile oil and oleoresins has also been investigated by GC–MS as the literature available is very scant.
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Chemicals
All chemicals and solvents used were of analytical grade. Thiobarbituric acid (TBA), DPPH and linoleic acid are of Acros (New Jersey, USA), butylated hydroxyl anisole (BHA), butylated hydroxyl toluene (BHT) and propyl gallate (PG) from SD Fine Chemicals Ltd. Mumbai; tween 20 and ferrozine from Merck Pvt. Ltd. Mumbai. The mustard oil was purchased from local oil mill, Gorakhpur, India.
Extraction of essential oil and oleoresins
The dry rhizomes of C. zedoaria were purchased from the local market of Gorakhpur, India and voucher specimens
Chemical investigations
Table 1 present relative composition of compounds in essential oil and oleoresins from C. zedoaria rhizome. A total of 60 components were identified in the essential oil. The major components were curzerenone (31.6%), germacrone (10.8%) and camphor (10.3%). In ethanol oleoresin, a total of 26 components were identified and the major ones are curzerenone (30.5%), germacrone (7.0%), camphor (5.5%) and curcumenol (4.4%). Twenty-five components were identified in isopropanol oleoresin and 40
Conclusions
According to the data obtained from the present study, essential oil of C. zedoaria rhizomes was found to be an effective antioxidant in-vitro assays when compared to standard antioxidant compounds such as BHA, BHT and PG. Isopropanol oleoresin was found to have potent antioxidant activity. These plant products can be promising alternatives of synthetic antioxidants for minimizing or preventing lipid oxidation and hence maintaining nutritional quality and prolonging the shelf life of foods.
Acknowledgments
We are thankful to the Head, Department of Chemistry, Deen Dayal Upadhyay Gorakhpur University for providing laboratory and spectral facilities. The financial support from the University Grants Commission to Pratibha Singh and Dr. Gurdip Singh (Emeritus Fellow) is also acknowledged.
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