Isolation and antioxidant activity of zeylaniin A, a new macrocyclic ellagitannin from Syzygium zeylanicum leaves.

Methanol extract obtained from Syzygium zeylanicum leaves exhibited potent antioxidant activity. The water extract obtained from this methanol extract by sequential extraction with hexane, chloroform, ethylacetate, and n-butanol also showed the strongest antioxidant activity among extracts. This water extract was further fractionated by column chromatography with various concentrations of methanol solutions. Among the 6 resultant fractions, the fraction developed with 20% methanol exhibited the most potent antioxidant activity. The one peak among the three major HPLC peaks in this fraction was isolated and purified using a preparative HPLC. The structure of a pure compound was elucidated as a novel macrocyclic ellagitannin using a (1)H/(13)C NMR and a high-resolution electrospray ionization mass spectrometer. This newly isolated compound, which was named zeylaniin A, exhibited potent antioxidant activities in the assays of DPPH, oxygen radical absorbance capacity, and malonadehyde/gas chromatography. S. zeylanicum leaves can be a possible source of natural antioxidants.