research papers Acta Cryst. (2021). C77, 505–512 https://doi.org/10.1107/S2053229621007841 505 Received 28 June 2021 Accepted 30 July 2021 Edited by A. G. Oliver, University of Notre Dame, USA Keywords: C. glutinosum; flavonoids; triter- penes; crystal structure; anthelmintic; natural product; absolute configuration. CCDC references: 2100535; 2100534 Supporting information: this article has supporting information at journals.iucr.org/c Anthelmintic flavonoids and other compounds from Combretum glutinosum Perr. ex DC (Combretaceae) leaves Placide M. Toklo, a Ele ´onore Yayi Ladekan, a * Anthony Linden, b * Sylvie Hounzangbe-Adote, c Sime ´on F. Kouam d and Joachim D. Gbenou a a Laboratoire de Pharmacognosie et des Huiles Essentielles, Faculte ´s des Sciences et Techniques, Universite ´ d’Abomey Calavi, 01 BP: 918 ISBA Cotonou, Benin, b Department of Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland, c Laboratoire d’Ethnopharmacologie et de Sante ´ Animale, Faculte ´ des Sciences Agronomiques, Universite ´ d’Abomey Calavi, 01 BP: 526 Cotonou, Benin, and d Department of Chemistry, Higher Teacher Training College, University of Yaounde I, PO Box 47, 4124 Yaounde, Cameroon. *Correspondence e-mail: eleoyayi@yahoo.fr, anthony.linden@chem.uzh.ch A chemical study of the hydro-ethanol extract of the leaves of Combretum glutinosum resulted in the isolation of nine compounds, including 5-demethyl- sinensetin (1), umuhengerin (2), (20S,24R)-ocotillone (3), lupeol (4), -sito- sterol (5), oleanolic acid (6), betulinic acid (7), corymbosin (8) and -sitosterol glucoside (9). Four compounds have been isolated for the first time from the genus Combretum [viz. (1), (2), (3) and (8)]. The crystal structures of flavonoid (2), C 20 H 20 O 8 , Z 0 = 2, and triterpene (3), C 30 H 50 O 3 , Z 0 = 1, have been determined for the first time; the latter confirmed the absolute configuration of native (20S,24R)-ocotillone previously derived from the crystal structures of related derivatives. The molecules of (3) are linked into supramolecular chains by intermolecular O—HO hydrogen bonds. The crude extracts obtained by aqueous decoction and hydro-ethanolic maceration, as well as the nine isolated compounds, were tested for their anthelmintic activity on the larvae and adult worms of Haemonchus contortus, a hematophage that causes parasitic disorders in small ruminants. The evaluated anthelmintic activity showed that the extracts at different doses, as well as all the compounds tested at 150 mg ml 1 , inhibited the migration of the larvae and the motility of the adult worms of the parasite compared with the phosphate buffer solution negative reference control. The best activity was obtained with flavonoids (1), (2) and (8) on both stages of the parasite. The flavones that showed good activity can be used for the further development of other derivatives, which could increase the anthelmintic efficacy. 1. Introduction Combretaceae are trees, shrubs or often lianas widely distributed in subtropical to tropical regions. This family consists of 18 genera, including 370 species of Combretum (Malgras, 1992; McGaw et al. , 2001, Amadou, 2004). These species are widely used in traditional medicine for their numerous pharmacological properties (Komlan, 2002). C. glutinosum is a tree of the genus Combretum belonging to the family Combretaceae. This plant is most often present in tree savannas, normally on shallow soils (Akoe ` gninou et al., 2006). It is distributed in tropical Africa from Mauritania to Uganda, passing through, for example, Senegal, Cameroon and Chad. In Be ´nin, the plant is spread in the North in Kandi, Ke ´tou, Toukountouna, south of Malanville, Bessassi and Porga, and in the Pendrari Park (Akoe ` gninou et al., 2006). This species is among the most widely used of the medicinal plants in West Africa (Kerharo & Adam, 1974). It has been reported by Toklo et al. (2021) that it is used in the treatment of malaria, ISSN 2053-2296