HPLC microfractionation of flavones and antioxidant (radical scavenging) activity of Saccharum officinarum L.

Abstract

The antioxidant activity of sugarcane (Saccharum officinarum L.) juice towards DPPH reagent was determined (EC50) and the main compounds with radical scavenging activity in juice and leaves extracts were identified by HPLC-UV/PAD analysis combined with HPLC microfractionation monitored by TLC using β-carotene and DPPH as the detection reagents. In sugarcane leaves, luteolin-8-C-(rhamnosylglucoside) (1) was the most important compound with radical scavenging activity; in sugarcane juice, the flavones diosmetin-8-C-glucoside (2), vitexin (3) schaftoside (9), isoschaftoside (10) and 4',5'-dimethyl-luteolin-8-C-glucoside (11) were the most relevant compounds. The content of juice flavonoids (0.241 ± 0.001 mg total flavonoids/mL juice), comparable to other food sources of flavonoids, suggest the potential of sugarcane as a dietary source of natural antioxidants. However, the low antioxidant ability of sugarcane juice (EC50 = 100.2 ± 2.6 g L-1) also points to the need for further studies about the dietary intake of sugarcane flavonoids and its effects on human health.

A atividade antioxidante do suco de cana-de-açúcar (Saccharum officinarum L.) frente ao reagente DPPH foi avaliada (EC50) e as principais substâncias com atividade seqüestradora de radicais livres do suco e extratos de folhas foram identificadas por CLAE-UV/DAD combinada com CLAE-microfracionamento monitorado por CCD, usando β-caroteno e DPPH como reagentes de detecção. As substâncias mais importantes com atividade seqüestradora de radicais livres foram: nas folhas, luteolina-8-C-(ramnosilglucosídeo) (1); no suco, as flavonas diosmetina-8-C-glucosídeo (2), vitexina (3), schaftosídeo (9), isoschaftosídeo (10) e 4',5'-dimetil-luteolina-8-C-glucosídeo (11). O conteúdo de flavonóides totais do suco (0,241 ± 0,001 mg flavonóides totais/mL suco), comparável ao de outras fontes de flavonóides, sugere o potencial da cana-de-açúcar como fonte alimentícia de antioxidantes naturais. Porém, a baixa capacidade antioxidante da garapa (EC50 = 100,2 ± 2,6 g L-1) indica a necessidade de estudos sobre o consumo na dieta e seus efeitos na saúde humana.