Two polymethoxylated flavonoids with antioxidant activities and a rearranged clerodane diterpenoid from the leaf exudates of Microglossa pyrifolia
View/ Open
Date
2014-12Author
Akimanya, Aggrey
Midiwo, Jacob O.
Matasyoh, Joseph
Okanga, Francis
Masila, Veronica M
Walker, Larry
Babu, L. Tekwan
Muhammad, Ilias
Omosa, Leonidah Kerubo
Language
enMetadata
Show full item recordAbstract
Three novel compounds; two polymethoxylated flavonoids, 5,7,4′-trihydroxy-3,8,3′,5′-tetramethoxyflavone (1), 5,7,3′-trihydroxy-3,8,4′,5′-trimethoxyflavone (2), and a clerodane diterpenoid; 8-acetoxyisochiliolide lactone (3) were characterized from the leaf exudates of Microglossa pyrifolia. In addition, three known polymethoxylated flavonoids including; 5,7,4′-trihydroxy-3,8,3′-trimethoxyflavone (4), 5,3′4′-trihydroxy-3,7,8-trimethoxyflavone (5), 5,3′4′-trihydroxy-7-methoxyflavanone (6) and a clerodane diterpenoid; 7,8-epoxyisocholiolide lactone (7) were identified. Their structures were determined on the basis of spectroscopic evidence. All the compounds did not exhibit antiplasmodial and antimicrobial activities at 47.6 μg/mL and were not cytotoxic at 5 μg/mL. Compound 6 exhibited modest antileishmanial activity with IC50 value of 13.13 μg/mL with 5 and 7 showing activities with IC50 values of 31.13 and 38.00 μg/mL, respectively, therefore inactive. The flavonoids (quercetin derivatives, 4 and 5) showed similar antioxidant activities, using 2,2-diphenylpicrylhydrazyl (DPPH) assay, with IC50 values of 6.2 ± 0.3 μg/mL for 4 (17.3 μM) and 5 (17.8 μM) respectively. These activities were comparable to that of the standard quercetin (IC50 value of 6.0 ± 0.2 μg/mL (19.9 μM)), irrespective of methylation of the characteristic hydroxyl groups expected to be responsible for activity and additional substitution at C-8 in ring A of the flavonoid ring. These studies revealed that the presence of an hydroxyl group at C-4′ positions and oxygenation at C-3 in flavone skeleton, appears to be necessary for good antioxidant activities as encountered in compounds 1, 4 and 5. Substantial reduction in antioxidant activity was shown by methoxylation of the 4′-OH as observed in compound 2 with an IC50 value of 8.79 ± 0.3 μg/mL (24.4 μM).
URI
http://www.sciencedirect.com/science/article/pii/S1874390014002511http://hdl.handle.net/11295/79436
Citation
Akimanya, A., Midiwo, J. O., Matasyoh, J., Okanga, F., Masila, V. M., Walker, L., ... & Omosa, L. K. (2014). Two polymethoxylated flavonoids and a rearranged clerodane diterpenoid with antioxidant activities from the leaf exudates of< i> Microglossa pyrifolia</i>. Phytochemistry Letters.Publisher
University of Nairobi