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FoodChemistryFood Chemistry 88 (2004) 243252www.elsevier.com/locate/foodchemFree radical-scavenging activity of organic extracts and of pureavonoids of Blumea balsamifera DC leavesFazilatun Nessa a,1, Zhari Ismail a,1, Nornisah MohamedMas Rosemal Hakim Mas Haris b,*aa,1,School of Pharmaceutical Sciences Universiti Sains Malaysia, 11800 Penang, MalaysiabSchool of Chemical Sciences, Universiti Sains Malaysia, 11800 Penang, MalaysiaReceived 17 June 2003; received in revised form 12 January 2004; accepted 12 January 2004AbstractPhytochemical investigation on the leaves of Blumea balsamifera DC resulted in the isolation of 11 avonoids. Their chemicalstructures were elucidated by means of elemental analyses and dierent spectroscopic methods, such as UV, IR, NMR and MS. Thefree radical scavenging activity of organic extracts of B. balsamifera DC leaves and that of pure avonoids isolated from the leaveswas evaluated using 1,1-diphenyl-2-picrylhydrazyl radical. A dose response curve was plotted for determining SC50 values (theconcentrations required to inhibit radical formation by 50%). The antioxidant activities of crude extracts decreased in the order:methanol extract > chloroform extract > pet-ether extract. The antioxidant activities of all compounds tested decreased in the order:quercetin > rhamnetin > luteolin > luteolin-7-methylether > L -ascorbic acid > blumeatin > butylated hydroxyanisole > 5,7,30 ,50 tetrahydroxyavanone > tamarix

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