Ryanoids, natural

Ryanodine and 9,21-dehydroryanodine are the principal insecticidal components and toxicants among 11 identified ryanoids in the botanical insecticide ryania. Their biological activity is attributed to block of the calcium release channel, which is conveniently measured as inhibition of pH]ryanodine binding in muscle and nerve preparations. Structure-activity relationships based on 10 natural ryanoids and 45 of their derivatives help define the conformation of the ryanodine binding site and the structural requirements for insecticidal activity and selective toxicity. 

The natural ryanoids are conveniently isolated from ryania by wet chloroform extraction and rotary chromatography on silica gel with chloroform/methanol/ aqueous methylamine followed by reverse phase HPLC with aqueous methanol (2,7,8). Ryanodine 0 and dehydroryanodine 0 are the major ryanoids, each making up 480-700 ppm (w/w) relative to the stem-wood, with seven other ryanoids contributing 10-64 ppm (w/w) each (8). 

Figure 1. Natural ryanoids (1-12, 14, 17, and 18) and their degradation products (13, 15, and 16). Ppm values or trace indicates content in a representative sample of ryania. A-G are literature designations for the natural products.

Structural assignments for the other natural ryanoids are based partially on degradations but primarily on NMR assignments (7,14,17). 

Cinncassiol (3-Deoxvrvanodoll Series. Nonester ryanoids from genera of Lauraceae include 6 from Persea indica where it occurs together with cinnzeylanol (7) (19,20). Alcohol 2 and its 10-acetate occur naturally in Cinnamomum zeylanicum Nees (21) and Cj, cassia (Chinese cinnamon) (22) in the latter case along with sets of ryanoids with skeletons corresponding to either the anhydro series 13 (22) or the diketo type... 

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See also in sourсe #XX -- [ , ]

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