High performance liquid chromatographic analysis of phenolic compounds and their antioxidant properties from different cultivars of Cyamopsis tetragonaloba (L.) Taub

Guar (Cyamopsis tetragonaloba (L.) Taub) is an annual legume plant and an important source of guar gum, which has great industrial and medicinal value due to phenolic compounds. Thus the consumption of guar and its products has been associated with a reduction in the risk of contracting some types of cancer and other chronic diseases. Phenolic compounds or polyphenols act as antioxidants with mechanisms involving both free radical scavenging and metal chelation. Thus, fifteen different cultivars of the cluster bean leaves i.e. Cyamopsis tetragonaloba (L.) Taub were evaluated for their content of phenolic acids and flavonoids using optimized high performance liquid chromatography (HPLC) with UV detection. These cultivars were also analyzed for antioxidant property using 1,1-diphenyl-2-picryl-hydrazyl (DPPH) activity. Rajasthan guar cultivar-1031 (RGC-1031) showed higher phenolic contents along with better antioxidant property. These results were also confirmed with HPLC where ten phenolic/flavonoid compounds were detected and quantified at varying levels in leaves of different cultivars of guar. Polyphenols such as sinapic acid, cholorogenic acid, caffeic acid, gallic acids and ferulic acid were detected with binary mode of pumps within 10 min with a flow rate of 1.0 mL/min where as flavanoids like kaempferol and myricetin were also identified showing variations among all cultivars. The total phenolic contents and total flavonoid contents in all cultivar were in the range 60.03 to 204.67 mg GAE/g and 4.26 to 12.43 mg QE/g, respectively. In particular, the cultivar RGC-1031 showed the highest content while Local-Selection showed the least content of the total polyphenols. Kaempferol was found to be major constituent in the studied guar cultivars than other phenolics. The extensive variability was observed in polyphenols among fifteen cultivars of guar. The Principal component analysis (PCA) showed that Local-Selection contained higher kaempferol and myricetin, while Pusa Selection-1 recorded higher cholorogenic acid and kaempferol.