Phenolic compounds isolated from Renealmia nicolaioides rhizomes

Renealmia L.f. comprises approximately 75 African and Neotropical species of herbaceous and rhizomatous plants from the family Zingiberaceae. Species from this genus have been used as food, and as medicinal plants. The chemical studies are scarce for the genus Renealmia. This study aims to identify special metabolites of the rhizome of Renealmia nicolaioides from the North Region of Brazil. The rhizomes were collected in June 2015, at the Catuaba Experimental Farm and the Humaitá Forest Reserve, both located in Rio Branco, state of Acre. The material was identified and a voucher 6646 was deposited in the herbarium of the Universidade Federal do Acre (UFACPZ). Air-dried powdered rhizomes were successively extracted with CH2Cl2 and CH3OH at room temperature and the residues of the extracts were partitioned with solvents. Chromatographic fractionation of fractions from the partition besides analyses of some fractions by 1H and 13C NMR, and mass spectra, [α]D, and CD allowed to identify four phenolic compounds. Three diarylheptanoids including a new compound (3), E-1,7-bis(4-hydroxyphenyl)-hept-1-en-3-one (1), 5R-1,7- bis(5-hydroxyphenyl)-(1E)-1-hepten-5-ol, (2), Rel-(1R,2R,5S)-2-hydroxy-1,7(p-hydroxyphenyl)-centrolobine (3), and one flavonoid, quercetin 3-methyl ether (4). The derivative 2a was used to confirm the structure of 2. All compounds are reported for the first time in this genus, and this is the first occurrence of compound 1 as a natural metabolite. Thus, the present study identifies Renealmia as a source of phenolic compounds and proposes new research for other species.