Resin glycosides from Ipomoea tyrianthina and their sedative and vasorelaxant effects.

The methanol-soluble extract from the root of Ipomoea tyrianthina was studied in order to isolate compounds with activity on the central nervous system and vasorelaxant effects. Chromatographic methods were used to isolate and purify seven new glycolipids (2-8). The structures of compounds 1-8 were elucidated by a combination of NMR spectroscopy and mass spectrometry. Tyrianthinoic acid (1) is a glycosidic acid composed of a linear pentasaccharide core bonded to a 11-hydroxyhexadecanoic acid. The structure of tyrianthinic acids III (2), IV (3), and V (4) consists of a partially acylated tyrianthinoic acid. Tyrianthinic acid VI (8) is a tetrasaccharide core bonded to a jalapinolic acid, acylated by a 2-methyl-3-hydroxybutanoic acid. Tyrianthins C (5), D (6), and E (7) are ester-type heterodimers of scammonic acid A with different acylating residues in the two monomeric units. The macrolactonization site was located at C-3 of the rhamnose unit. The position of the ester linkage for monomeric unit B on the macrocyclic unit A was established at C-4 of the terminal quinovose. Compounds 5-7 increased the sleeping time induced by pentobarbital and the release of gamma-aminobutyric acid in brain cortex. In addition, compounds 5-7 showed significant in vitro relaxant effects on aortic rat rings, in endothelium- and concentration-dependent manners.

Intraspecies variation in the venom of the rattlesnake Crotalus simus from Mexico: different expression of crotoxin results in highly variable toxicity in the venoms of three subspecies.

The composition and toxicological profile of the venom of the rattlesnake Crotalus simus in Mexico was analyzed at the subspecies and individual levels. Venoms of the subspecies C. s. simus, C. s. culminatus and C. s. tzabcan greatly differ in the expression of the heterodimeric neurotoxin complex 'crotoxin', with highest concentrations in C. s. simus, followed by C. s. tzabcan, whereas the venom of C. s. culminatus is almost devoid of this neurotoxic PLA2. This explains the large variation in lethality (highest in C. s. simus, which also exerts higher myotoxicity). Coagulant activity on plasma and fibrinogen occurs with the venoms of C. s. simus and C. s. tzabcan, being absent in C. s. culminatus which, in turn, presents higher crotamine-like activity. Proteomic analysis closely correlates with toxicological profiles, since the venom of C. s. simus has high amounts of crotoxin and of serine proteinases, whereas the venom of C. s. culminatus presents higher amounts of metalloproteinases and crotamine. This complex pattern of intraspecies venom variation provides valuable information for the diagnosis and clinical management of envenoming by this species in Mexico, as well as for the preparation of venom pools for the production and quality control of antivenoms. BIOLOGICAL SIGNIFICANCE: This study describes the variation in venom composition and activities of the three subspecies of Crotalus simus from Mexico. Results demonstrate that there is a notorious difference in these venoms, particularly regarding the content of the potent neurotoxic phospholipase A2 complex 'crotoxin'. In addition, other differences were observed regarding myotoxic and coagulant activities, and expression of the myotoxin 'crotamine'. These findings have implications in, at least, three levels: (a) the adaptive role of variations in venom composition; (b) the possible differences in the clinical manifestations of envenomings by these subspecies in Mexico; and (c) the design of venom mixtures for the preparation of antivenoms effective in the neutralization of the venoms of the three subspecies.

Tyrianthinic acids from Ipomoea tyrianthina and their antimycobacterial activity, cytotoxicity, and effects on the central nervous system.

Four new partially acylated tetrasaccharides of 11-hydroxyhexadecanoic acid (1-4) were isolated from a methanolic extract of Ipomoea tyrianthina. The structures of these compounds were elucidated by spectroscopic and chemical methods. The resin glycoside composition of I. tyrianthina varied with the location of growth in Mexico. Compounds 1-4 showed antimycobacterial activity, were cytotoxic against the KB cell line, and, in a mouse model, exhibited potentiation of hypnosis induced by pentobarbital, protected against seizures induced by pentylenetetrazole, and released GABA and glutamic acid.