Tricalysiosides P-U: Ent-kaurane Glucosides and a Labdane Glucoside from Leaves of Tricalysia dubia OHWI

Abstract

The approximately 50 species of Tricalysia (Syn. Canthium) are found in subtropical and tropical areas of Asia and Africa. Some species are used for medicinal purposes, e.g. the roots, leaves, and stem bark of Canthium subcordatum are used as folk medicines in Africa. 1)Tricalysia dubia (LINDL.) OHWI (Rubiaceae) is an evergreen shrub or tree that grows to a height of about 2-4 m. It is distributed in the south of China, Taiwan, and Okinawa. 2)In the course of our study on Okinawa's promising resource plants, the constituents of the title plant, T. dubia, were investigated.In previous papers, the structural elucidation of seven rearranged ent-kaurane glucosides, tricalysiosides A-G, and eight ent-kaurane glucosides, named tricalysiosides H-O, from leaves of T. dubia was reported.3,4) Non-glycosidic rearranged ent-kauranes were also isolated from the same plant species. 5,6) Further extensive investigation of the same plant material afforded five new ent-kaurane glucosides (4-8) and one new labdane glucoside (9), together with one megastigmane glucoside, two monoterpene glucosides (1, 2), [7][8][9] and sammangaoside B (3).10) This paper deals with their structural elucidation and revision of the stereostructure of sammangaoside B. Results and DiscussionAir-dried leaves of T. dubia were extracted with MeOH three times and the concentrated MeOH extract was partitioned with solvents of increasing polarity. The 1-BuOH-soluble fraction was separated by various chromatographic procedures including column chromatography (CC) on a highly porous synthetic resin (Diaion HP-20), normal silica gel and reversed-phase octadecyl silica gel (ODS) CC, then droplet counter-current chromatography (DCCC) to afford six diterpenoid glucosides, named tricalysiosides P-U (4-9) (Fig. 1), together with one megastigamne glucoside, two monoterpene glucosides (1, 2), [7][8][9] and summangaoside B (3).10) The details and yields are given in the Experimental section. The structures of tricalysiosides P-U (4-9) were elucidated by spectroscopic analyses and comparison with tricalysiosides previously isolated based on spectroscopic evidence. Sammangaoside B (3), [a] D Ϫ35.0°, was first isolated from Clerodendrum inerme but the stereochemistry of its six-membered ring portion remained to be determined. Phase-sensitive NOE experiments supported the previously reported relative structure of the ring system, as depicted in the literature. 10) Application of modified Mosher's method 11) to the aglycone led to revision of the absolute configuration of the 9-position to S (Fig. 2) Further extensive isolation work on the 1-BuOH-soluble fraction of a MeOH extract of Tricalysia dubia afforded five new ent-kaurane glucosides (4-8) and one new labdane glucoside (9), together with a known megastigmane glucoside, sammangaoside B (1), and monoterpene glucosides (2, 3). The structures of the new compounds were elucidated by analyses of one-and two-dimensional NMR spectroscopic data. The absolute configuration of the 9-position of sammangaoside B was revised to ...

Indiosides G–K: Steroidal Glycosides with Cytotoxic and Anti-inflammatory Activities from Solanum violaceum

“…Only two additional furostanols, anguivioside XI 17 and solasodoside F, 18 with a deformed F ring have been reported previously. The nine known constituents were isolated previously from different genera of Solanaceae (Lycium chinense), 9 Arecaceae (Borassus f labellifer 5 and B. decumbens 6 ), Rubiaceae (Tricalysia dabia), 10 and Urticaceae (Urtica dioica) 7 families, but are first reported herein from S. violaceum.…”

Microtropiosides A–F: ent-Labdane diterpenoid glucosides from the leaves of Microtropis japonica (Celastraceae)

“…2). Comparison of the carbon shifts of C-2 and C-3 of 1 with those of the labdane 3-O-glucoside, tricalysioside U (8) (Otsuka et al, 2007) and the ent-labdane 3-O-glucoside (9) (Shen et al, 2006) (Table 1) clearly showed that microtropioside A belonged to the ent-labdane series. The configuration of the C-14 hydroxyl group was deduced to be  on the basis of significant NOE interactions between H-11 axial and H-14.…”

A Study on the Lipase-catalysed Acylation of 6,7-Dihydroxy-linalool

“…The monoterpene linalool and a number of its hydroxylated derivatives are secondary metabolite occurring in different vegetal species [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. Although both enantiomeric forms of linalool are present in nature, (R)-linalool (1), its 6,7-dihydroxylated derivatives (2a-5a) and a number of their glycoside derivatives ( Figure 1) are more common than the corresponding (S)-linalool deriving monoterpenes.…”