Withanolides occurrence

Comparison of the structure of jaborosalactone 2 (85) with that of trechonolide A (64) indicated that both compounds may have closely related biosynthetic precursors. In the former withanolide, ring closure on C-12 has occurred with a C-22 hydroxyl as shown in Fig. (4) pathway a. Oxidation of this intermediate or a related compound to the 22-ketone would allow cyclization between C-23 and the C-12 ketone to give a spiranoid withanolide (Fig. (4) pathway b). The co-occurrence of trechonolide A (64) and jaborosalactone 2 (85) in J. araucana supports this hypothesis. 

Nittala SS, Lrolow L, Lavie D(1981) Novel occurrence of 14 J-hydroxy group on a withanolide skeleton X-Ray crystal and molecular structure of 14 J-hydroxywithanone. J Chem Soc Chem Commun 4 178... 

Non-solanaceous Occurrence. Withanolides have been discovered also in certain Tacca spp. of the Taccaceae (taccalonolides Huang et al. 2002) and Ajuga spp., e.g., A. parviflora Benth., Lamiaceae (ajugins Khan et al. 1999) as well as in some marine organism. Nevertheless, their occurrence in the Solanaceae is predominating by far. 

There is only one report on the occurrence of withanolides out of the Solanoideae, namely in Browallia viscosa ( 0.02% nicandrenone and traces of withaferin A Rozkrutowa 1987). Therefore, it would be useful if this exceptional result - from the chemotaxonomic point of view - could be confirmed. 

Co-occurrence of lactol-type withasteroids and steroidal alkaloids/glycoalkaloids has been demonstrated in two Solamm spp. S. ciliatum, S. sisymbrifolium). However, there is no report on co-occurrence of these alkaloids and withanolides. In a few taxa even withanolides co-occur surprisingly with different types of tropane alkaloids, i.e., hyoscyamine-type tropanes fowDatura spp., Hyoscyamus niger) or non-hyoscyamine-type tropanes and related alkaloids Nicandra physalodes, Physalis alkekengi, P. peruviana, Withania somnifera) for details see Tables 3.1 and 3.8. 

---