New C28 Steroidal Glycosides from Tubocapsicum anomalum

Abstract

Tubocapsicum anomalum is a plant widely distributed in China, India, the Philippines, and Japan. It has antigonorrhel, antifuruncular, antiinflammatory, and antiintumescent effects.1) Previously, as a part of studies on the steroidal glycosides in solanaceous plants, two novel C 28 steroidal lactone glycosides, tubocaposides A and B, were isolated from the fresh fruit of T. anomalum and their structures determined using X-ray diffraction analysis.2) Following that study, we also reported isotubocaposides A, B, and C from the fresh fruit of this plant. 3)Continuing research on this plant led to the isolation of two new steroidal glycosides, tuboanosides A (1) and B (2). They were isolated from the MeOH extract of the aerial parts of T. anomalum by a combination of high porous resin , and normal-and reversephase silica gel column chromatography.The sapogenol moiety of these two glycosides was also regarded as an ergostane derivative by comparison with the NMR spectrum of tuboanosigenin (3) obtained by enzymatic hydrolysis of tuboanoside A (1). The sapogenol in turn was derivatized into a p-bromobenzoyl derivative (4) to afford colorless prisms. The derivative was subjected to X-ray analysis to establish its structure. This report describes the structural characterization of tuboanosides A (1) and B (2).Tuboanoside A (1) 71.8, 71.7 (2ϫC-4), 78.4, 78.3 (2ϫC-5), 62.8, and 63.0 (2ϫC-6) and a 2,6-di-O-sugar-substitued glucopyranosyl moiety 4) (glc) at d 101.0 (C-1), 84.6 (C-2), 77.6 (C-3), 71.3 (C-4), 76.9 (C-5), and 69.9 (C-6). After deducting these signals originating from sugar, the remainder totals 30 carbon signals including one acetyl group. Therefore the sapogenol was regarded as an ergostane derivative, which comprised four oxygen-bearing carbons at d 71.0, 74.3, 75.3, and 77.8, one lactone carbonyl group at d 177.8, and one acetyl group at d 21.1 and 170.5. The structure of this new sapogenol was deduced to be similar to that of tubocaposide, 2) although there were some differences in the substitution moiety at C-17 in the (Fig. 1) of 3 enabled the assignment of 1 H-and 13 C-NMR signals to provide a planar structure for 3.Next, the sapogenol (3) was derivatized into a p-bromobenzoate (4) by reaction with p-bromobenzoyl chloride and pyridine at room temperature.6) The benzoate obtained as colorless prisms, mp 162-163°C, [a] D Ϫ31.9°(CHCl 3 ), had the molecular formula C 37 H 47 BrO 7 based on positive-ion FAB-MS. The 1 H-NMR spectrum of 4 showed a multiplet signal at d 5.45 down-shifted by 1.58 ppm from that of 3 and A 2 B 2 aromatic proton signals at d 7. 71, 8.06 (each 2H, d, Jϭ 8.6 Hz). Therefore 4 was characterized as a 3-O-p-bromobenzoate of tuboanosigenin. The X-ray analysis of 4 is shown in Fig. 2. Two new C 28 steroidal glycosides, tuboanosides A (1) and B (2), were isolated from the fruit of Tubocapsicum anomalum MAKINO. Their chemical structures were elucidated on the basis of spectroscopic and X-ray diffraction analysis of the p-bromobenzoyl derivative (4) of tuboanosigenin (3), the sapogenol deri...

Withanolides with Antibacterial Activity from Nicandra john-tyleriana

“…The 1 H and 13 C NMR spectra of compound 8 were run in pyridine-d 5 in order to correlate the chemical shifts with those of tuboanosigenin pbromobenzoate, a compound for which X-ray analysis has been performed. 18 The observed differences between both spectra were in good agreement with compound 8 having the opposite configuration at C-24 (Table 2). Accordingly, the structure of 8 was elucidated as (17R,20S,22R,24S,25R)-5β,6β-epoxy-16α,24α-dihydroxy-21,25-cycloergost-2-en-1-one.…”

“…Thus The three withanolide subtypes found in N. john-tyleriana, namely, withanolides with an unmodified skeleton, acnistins, and withajardins, are the same as those isolated from Tubocapsicum anomalum but distinct from those isolated from N. physalodes. 16,18 In the latest phylogenetic classifications for the family Solanaceae, 19,20 none of these genera have been placed in any particular tribe. It would be premature to use the present phytochemical evidence to draw any chemotaxonomic conclusions at the present time.…”

Natural withanolides: an overview

“…This is the first report of a natural withanolide from the Myrtaceae family. Larnaxolides A (113) and B (114), obtained from Larnax glabra leaves, have an epoxylactol side chain. They are 5-epimers, 69 and larnaxolide B ( 114) is an uncommon 5b-hydroxy-6a,7a-epoxy derivative.…”

Withanolides and Related Steroids

“…Withajardins A-E (277-281) were isolated from plants of Deprea orinocensis collected in Colombia (129,130). A 16,17-dihydroxylated withajardin, tubonolide A (282), was isolated from the stems and leaves of T. anomalum (107) and the glycosides tuboanosides A and B (283 and 284) from the fruits of this same plant (131). The latter three compounds have an inverted configuration at C-24 compared to the other withajardins, and this was confirmed by X-ray diffraction in the case of tuboanosides A and B (Fig.…”