Biochemical Systematicsand Ecology, Vol. 18, No. 7/8, pp. 529-532, 1990. 0305-1978/90$3.004-0.00 Printed in GreatBritain. © 1991 PergamonPressplc. Flavonoid Systematics of Ten Sections of Ludwigia (Onagraceae) JOHN E. AVERETT,* ELSA M. ZARDINIt and PETER C. HOCHT~ *National Wildflower Research Center, Austin, TX 78725, U.S.A.; 1Missouri Botanical Garden, P.O. Box 299, St Louis, MO 63166, U.S.A. Key Word Index--Ludwigia, Onagraceae; flavonoids; glycoflavones; flavonols; phytochamical evolution. Abstract--Data for the flavonoids of 19 species in 10 sections of Ludwigia are presented. Eight flavonoids, comprising four glycoflavones, of which vitexin and isovitexin are reported for the first time in Ludwigia, and four flavonol glycosides, based on quercetin, are present in these species. Each section treated here has either glycoflavones or flavonols; presence of only one class is considered to be advanced in the genus as a whole, compared with the presence of both glycoflavones and flavonols in the more generalized sects Myrtocarpus, Cinerascentes, and Pterocaulon, which were examined earlier. Only glycoflavones are present in sects Macrocarpon (four species), Serninuda (five species), the ditypic African sect. Africana, the monotypic African sects Brenania, Cryptosperma, and Prieurea, the monotypic east Asian sect. Nipponia, and the monotypic pantropical section Fissendocarpa. Only flavonols are present in the monotypic Old World section Caryophylloidea and sect. Oligo- spermum, which comprises nine species widespread in the Old and New Worlds. Introduction As a continuation of a comprehensive study of the flavonoids of Onagraceae [1], we here report results for 10 sections of Ludwigia. We previously reported data from 30 species in seven other sections of the genus [2], which included those groups considered to be most generalized [3-5]. Ludwigia is one of the largest and most diverse genera in the family Onagraceae, with some 82 species grouped in 23 sections [6, 7]. Recent data indicate that Ludwigia, which is very distinctive within the family and comprises the only genus of the tribe Jussiaeeae, constitutes the sister group of all other Onagraceae [4, 8-10]. The 10 well-delimited sections investigated here are considered to be specialized in many features [6]. Six of these sections are monotypic and comprise autogamous herbs; three of them (Brenania, Cryptosperma, and Prieurea) are restricted to tropical Africa, one to east Asia (Nipponia), one is widely distributed in the Old World (Caryophylloidea), and one is a pantropical weed (Fissendocarpa). The ditypic sect. Africana, is also restricted to Africa. The remaining three sections are larger, with broad distributions. Section Macrocarpon consists of four species of tTo whom correspondence should be addressed. (Received 8 June 1990) herbs or low shrubs, three of which grow pri- marily in southern South America, whereas the fourth, L. octovalvis (Jacq.) Raven, is a highly polymorphic, pantropical, autogamous weed. Section Seminuda includes five species of robust herbs, two of which occur only in the New World, one [L. africana (Brenan) Hara] only in West Africa, and two common to Latin America and Africa [6]. Finally, sect. Oligospermum is a widespread polyploid complex comprising nine species, of which two are endemic to the Old World, five to the New World, and two occur in both regions (Zardini and Raven, unpublished data). Results Eight flavonoids were found to be present among the species sampled (Table 1): vitexin (1), isovitexin (2), orientin (3), isoorientin (4), quercetin 3-rhamnoside (5), quercetin 3-arabino- side (6), quercetin 3-glucoside (7), and quercetin 3-rutinoside (8). Compounds 1-4 are glyco- flavones and 5-8 are flavonol glycosides. Com- pounds 1 and 2 have not been reported pre- viously in Ludwigia [2]. On the other hand, the glycoflavone orientin-O-acylate and the flavonol quercetin 3-diglucoside, which were detected in sects Cinerascentes, Heterophylla, and Ptero- caulon, and in sects Myrtocarpus and Ptero- caulon, respectively [2], were not detected in the 529