{"references": ["1. Williams HK. Molecular pathogenesis of oral squamous carcinoma: Mol Pathol. 2000; 53:165-172. 2. Choudhari SK, Chaudhary M, Gadbail AR, Sharma A, Tekade S. Oxidative and antioxidative mechanisms in oral cancer and precancer: a review. Oral Oncol. 2014; 50(1): 10-8. 3. Evans LW, Omaye ST. Use of Saliva biomarkers to monitor efficacy of vitamin C in exercise-induced oxidative stress. Antioxidants. 2017; 6(5): 1-21. 4. Al-Tarawneh SK, Border MB, Dibble CF, Bencharit. D e fi n i n g s a l i v a r y b i o m a r k e r s u s i n g m a s s spectrometry-based proteomics: a systematic review.", ". 5. Nair A, Nair BJ. Comparative analysis of the oxidative stress and antioxidant status in type II diabetics and nondiabetics: A biochemical study J Oral Maxillofac Pathol Dec. 2017;21(3):394-401. 6. Karthik B, Shruthi DK, Singh J, Tegginamani AS, Kudva S. Do tobacco stimulate the production of nitric oxide by up regulation of inducible nitric oxide synthesis in cancer: Immunohistochemical determination of inducible nitric oxide synthesis in oral squamous cell carcinoma - A comparative study in tobacco habituers and non-habituers. J Can Res Ther. 2014;10:244-50. 7. Desai AP, Desai S. UV spectroscopic method for determination of vitamin C (ascorbic acid) content in different fruits in south Gujarat region. Int J Environ S c i N a t R e s . 2 0 1 9 ; 2 1 ( 1 ) : 4 1 - 4 4 . d o i : 10.19080/IJESNR.2019.21.556056 8. Isola G, Polizzi A, Muraglie S, Leonardi R, Giudice AL. Assessment of vitamin C and antioxidant profiles in saliva and serum in patients with periodontitis and ischemic heart disease.Nutrients 2019;11:1-13. doi:10.3390/nu11122956 . 9. Mutalik S. Measurement of glutathione, ceruloplasmin, and malondialdehyde in oral leukoplakia, oral sub mucous fibrosis and oral cancer. Master thesis. RGUHS, Bangalore. 10. Almadori G, Bussu F, Galli J, Limongelli A, Persichilli S, Zappacosta B, et al. Salivary glutathione and uric acid levels in patients with head and neck squamous cell carcinoma. Head and Neck. 2007;29(7):648-654. 11. Parmar M, Pandhi N, Patel P. Clinical evaluation of sialic acid in head and necksquamous cell carcinoma patients and tobacco chewers or smokers with no cancer. Biomed Pharmacol J. 2017;10(4):2027-2033. 12. Juneja S, Rathore AS, Sharma K, Shetty D, Jain A. Antioxidant-oxidant index as a biomarker in oral potentially malignant disorders and oral squamous cell carcinoma: a biochemical study. J Clin Diagn Res. 2017;11(3):05-08. 13. Frei B, England L, Ames BN. Ascorbate is an outstanding antioxidant in human blood plasma. Proc. Nati Acad Sci. USA. 1989;86:6377-6381. 14. . Rajaram S, Danasekaran BP, Venkatachalapathy R, Prashad KV, Rajaram S. N-acetylneuraminic acid: A scrutinizing tool in oral squamous cell carcinoma diagnosis. Dent Res J. 2017; 14: 267-71", "OMICS. J Integ Biol. 2011; 15(6): 353-361"]}

Background-Oxidative stress in biological systems is a complex process that is characterized by an inequity between the production of free radicals (FR) and the ability of the body to eliminate these reactive species through the use of endogenous and exogenous antioxidants. The pathogenesis of oral cancer has been linked to alterations in the antioxidant defense mechanism. Materials & Methods- Saliva from twenty patients with OSCC, forty patients with OPMDs and twenty healthy subjects in the age group of thirty five to seventy five years was analyzed for levels of nitric oxide, vitamin C, total sialic acid and GSH using spectrophotometry. Results - The levels of salivary vitamin C and glutathione were significantly reduced and those of nitric oxide and sialic acid were raised in patients having OPMD's and oral squamous cell carcinoma. The corelation between the AOI and calculated ratios indicated that antioxidant potential of the saliva was decreased and was statistically related to (p <0.001) development of OPMD, which further may progress to oral cancer, notably OSCC. Conclusion- The current study demonstrated that the estimation of vitamin C, nitric oxide, sialic acid and GSH in saliva could be used as an early potential diagnostic biomarker in the screening of oral cancer. The antioxidant-oxidant indices (AOI's) can be used as a reliable tool for predicting the oral microenvironment and its predicted change towards development of oral cancer. This optimized developed protocol was also found to be simple and cost effective.