A chalcone and a dihydrochalcone from Uvaria dulcis Kan Chantrapromma a, *, Yanisa Rat-A-pa a , Chatchanok Karalai a , Vitchu Lojanapiwatana a , Vatcharee Seechamnanturakit b a Department of Chemistry, Faculty of Science, Prince of Songkla University, Hatyai, Songkhla 90112, Thailand b Scienti®c Equipment Centre, Prince of Songkla University, Hatyai, Songkhla 90112, Thailand Received 30 April 1999; received in revised form 16 July 1999 Abstract 2 ',3 '-Dihydroxy-4 ',6 '-dimethoxychalcone and the corresponding dihydrochalcone were isolated from the leaves of Uvaria dulcis and characterized by chemical and spectral methods. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Uvaria dulcis; Annonaceae; Chalcone; Dihydrochalcone; Flavanone 1. Introduction The genus Uvaria has been a rich and varied source of new compounds as is evidenced by the isolation of alkaloids (Panichpol, Waigh & Waterman, 1977; Achenbach & Roelsberger, 1979) ¯avonoids (Cole, Torrance, Wiedhopf, Arora & Bates, 1976; Lasswell & Huord, 1977; Okorie, 1977; Tammami, Torrance, Fabela, Wiedhopf & Cole, 1977; Huord, Lasswell, Hirotsu & Clardy, 1979; Huord & Oguntimcin, 1982), cyclohexene oxides (Holbert et al., 1979; Schulte, Ganem, Chantrapromma, Kodpinid & Sub- suansri, 1982) and aromatic oils (Kodpinid, Thebtara- nonth & Thebtaranonth, 1985). In continuation of our studies on the genus Uvaria (Holbert et al., 1979; Schulte et al., 1982; Chantrapromma, Pakawatchai, Shelton, White & Worapatamasri, 1989), we further examined the leaves of U. dulcis Dunal. We now report on the chemical examination of the leaves which gave a chalcone 1 and its corresponding new dihydrochalcone 2 together with ¯avanone 3 and ben- zyl benzoate. 2. Results and discussion Hot hexane extract of the leaves of U. dulcis aorded a gum which was chromatographed on silica gel using increasing percentages of chloroform in hexane to give three compounds. The ®rst, an oil, MS gave M.W 212 analysing for C 14 H 12 O 2 was found to be benzyl benzoate by detailed examination of IR, NMR, MS spectral data and by comparison with an authentic sample. The second compound, mp 124±1268C, was obtained as red crystals and identi®ed as 2 ',3 '-dihydroxy-4 ',6 '-dimethoxychalcone 1 on the basis of UV, NMR, MS data and chemical interconversions. The UV spectrum in MeOH supports a chalcone structure of the compound (Panichpol et al., 1977; Mabry, Markham & Thomas, 1970), l max 240, 290 and 346 nm. The lack of a shift in Band II in NaOAc indicates that the A-ring 4 ' position is substituted. A bathochromic shift of Band I in AlCl 3 relative to the MeOH spectrum of 34 nm (from 346 to 380 nm) suggests a free hydroxyl group at the 6 ' position in the A-ring. NMR data establish an unsubstituted B-ring; a multiplet at d 6.85±7.75 inte- grating for ®ve aromatic protons which can be assigned to the B-ring and at d 7.90 to the a- and Phytochemistry 53 (2000) 511±513 0031-9422/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0031-9422(99)00477-X www.elsevier.com/locate/phytochem * Corresponding author.