Antioxidant and Nitrite-Scavenging Capacities of Phenolic Compounds from Sugarcane (Saccharum officinarum L.) Tops

Sugarcane tops were extracted with 50% ethanol and fractionated by petroleum ether, ethyl acetate (EtOAc), and n-butyl alcohol successively. Eight phenolic compounds in EtOAc extracts were purified through silica gel and Sephadex LH-20 column chromatographies, and then identified by nuclear magnetic resonance and electrospray ionization mass spectra. The results showed that eight phenolic compounds from EtOAc extracts were identified as caffeic acid, cis-p-hydroxycinnamic acid, quercetin, apigenin, albanin A, australone A, moracin M, and 5'-geranyl-5,7,2',4'-tetrahydroxyflavone. The antioxidant and nitrite-scavenging capacities of different solvent extracts correlated positively with their total phenolic (TP) contents. Amongst various extracts, EtOAc extracts possessed the highest TP content and presented the strongest oxygen radical absorbance capacity (ORAC), 1,1'-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging capacity, 2,2'-azobis-3-ethylbenthiaazoline-6-sulfonic acid (ABTS) radical-scavenging capacity, ferric reducing antioxidant power (FRAP) and nitrite-scavenging capacity. Thus, sugarcane tops could be promoted as a source of natural antioxidant.