Structurally Unique Biflavonoids from Selaginella chrysocaulos and Selaginella bryopteris

Abstract

Chemical investigation of Selaginella chrysocaulos from Northeast India yielded three new (i.e., 1-3) and two known biflavonoids. From Selaginella bryopteris, collected in the southern part of India, one new (11) and eleven known biflavonoids of the amentoflavone- and hinokiflavone-type were isolated and identified. The structures of the compounds were elucidated by 1D- and 2D-NMR spectroscopy, and by mass spectrometry. The absolute configurations of chiral biflavonoids with flavanone subunits (from S. bryopteris) were determined with the aid of circular-dichroism (CD) spectroscopy. Several very rare or even unprecedented substructures in biflavonoids were found.

Phenolic Compounds from Selaginella moellendorfii

“…C) Me(ring A)/C(5), Me(ring A)/C(6), and Me(ring A)/C(7), and correlations Me(ring B)/C(5''), Me(ring B)/C(6''), and Me(ring B)/C(7''). The characteristic C-atom signals at d(C) 142.3 (s, C(3')), 121.4 (d, C(2')), and 161.3 (s, C(4''')) indicated that two flavones were linked at C(3') and C(4''') with an O-bridge, as in ochnaflavone (10). The assignment of proposed linkage at C(3') was also supported by the HMBC peaks HÀC(2')/C(3) and HÀC(5')/C(3').…”

“…Etherification of two apigenins between C(3') and C(4''') leads to ochnaflavone (10), and methylation of 10 affords 6-methylflavone-5,7,4'-triol-(3' ! O !…”

Antiplasmodial and leishmanicidal activity of biflavonoids from Indian Selaginella bryopteris

“…These were tested against T. b. rhodesiense STIB 900, T. cruzi Tulahuen strain C2C4, L. donovani strain MHOM-ET-67 and P. falciparum K1 (Table 1). The EtOAc fraction showed the highest activity and was further selected for the isolation of twelve pure compounds described in Swamy et al (2006). The modest activity of the EtOAc fraction against A series of eleven biflavonoids containing amentoflavone and hinokiflavone derivatives from the Indian medicinal herb Selaginella bryopteris has been investigated for their antiprotozoal activity using in vitro assays against the K1 strain of Plasmodium falciparum, Leishmania donovani, Trypanosoma brucei rhodesiense and Trypanosoma cruzi.…”

“…For the interpretation of this finding, bioavailability studies are needed. Isolation and structural determination of the eleven biflavones from S. bryopteris is described in Swamy et al (2006).…”

“…The highest antiprotozoal activity was found for 7,4 0 ,7 00 -tri-Omethylamentoflavone (11), a minor compound in S. bryopteris (Swamy et al, 2006). To study the in vivo activity of 11 in a Plasmodium berghei NMRI mouse model, we used a semisynthetic approach to convert amentoflavone (1) into a mixture of predominantly tri-O-methylated derivatives.…”