Table 1.

Examples of major SAs

Major types of SAs	Origin	Instances	Brief Chemistry of the representatives
Salamandra	Amphibians	Cycloneosamandione	In this type of steroidal alkaloid, the ring‐A is altered, commonly into aza‐homosteroids, except for Cycloneosamandione.
Jerveratrum	Solanaceae, mainly found in food crops like potatoes, tomatoes	Jervine	Here the side‐chain of a C27 steroid has been transformed into a piperidine ring.
Spirosolane		Soladulcidine
Solanidine		Rubijervine	In this type, an extra ring is formed by C‐16 to N bond formation.
Cerveratrum	Monocot families such as the Orchidaceae	Cevane	In this type of steroidal alkaloid, an abeo shift occurs from a procevine‐type precursor, where the D ring has been expanded at the expense of the C ring. A widespread stereochemical difference has been observed within the basic cevane skeleton.
Conanine	Apocynaceae	Kurcholessine	Here almost all of the bases comprise an amino or an oxygen function at C‐3 position. Some differences are observed in their skeletons such as methylation at the C‐4 position.
Buxus		Cortistatin	This type of steroidal alkaloid is one of the largest groups, where the maximum structures are pentacyclic 4, 4, 14‐trimethyl‐9, 19‐cyclopregnanes. Some of this group posses a tetracyclic system where the 9, 10 bond has been fused to give a seven‐membered ring B. In some representatives, one or both carbon atoms attached to C‐4 have been lost. Presence of a nitrogen function at C‐3 and/or C‐20 has been observed, which may be partially methylated, fully methylated or unmethylated. Slight structural differences remain to be isolated from various Buxus spp. In this group, the suffix letters used in the nomenclature designate the degree of methylation of the nitrogen atom(s).
Pregnane	Apocynaceae, Buxaceae and Didymelaceae		In this type, major representatives contain an amino group or related functional groups at C‐3 or C‐20, and regularly at other positions .
Cephalostatins/ ritterazines	marine worm Cephalodiscus gilchristi (Cephalostatin 1) and tunicate Ritterella tokioka (Ritterazine A)	Cephalostatin 1, Ritterazine A	The cephalostatin 1 structure is categorized by an asymmetric blending of the central pyrazine ring with two extremely oxygenated steroidal spiroketal subunits. In ritterazine A, the left half is similar to that of cephalostatin 7, excluding an additional C‐7′ hydroxyl group. In the right half, the steroidal nucleus is totally rearranged.
Assorted steroidal alkaloids, including non‐nitrogenous steroids connected by an ester or acetal bond to a nitrogen‐containing unit	Marine sponges, toads,	Plakinamines, bufotoxin	In this group, the ester or acetal bond act as a linker between non‐nitrogenous steroids and the nitrogen containing unit.

Abbreviation: SA, steroidal alkaloid.