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The camphor content of sage (Saivia officinalis L.) leaves increases as the leaves expand, and the increase is roughly proportional to the number of filled peltate oil glands which appear on the leaf surface during the expansion process. "4CO2 is more rapidly incorporated into camphor and its direct progenitors in expanding leaves than in mature leaves, and direct in vitro measurement of the key enzymes involved in the conversion of geranyl pyrophosphate to camphor indicates that these enzymes, including the probable rate-limiting cyclization step, are at the highest levels during the period of maximum leaf expansion. These results clearly demonstrate that immature sage leaves synthesize and accumulate camphor most rapidly.

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A radiation-induced mutant of Scotch spearmint (Mentha x graclis) was shown to produce an essential oil containing principally C3-oxygenated p-menthane monoterpenes that are typical of peppermint, instead of the CS-oxygenated monoterpene family characteristic of spearmint. In vitro measurement of all of the enzymes responsible for the production of both the C3-oxygenated and CS-oxygenated families of monoterpenes from the common precursor (-)-limonene indicated that a virtually identical complement of enzymes was present in wild type and mutant, with the exception of the microsomal, cytochrome P-450-dependent (-)-limonene hydroxylase; the C6-hydroxylase producing (-)-trans-carveol in the wild type had been replaced by a C3-hydroxylase producing (--trans-isopiperitenol in the mutant. Additionally, the mutant, but not the wild type, could carry out the cytochrome P-450-dependent epoxidation of the ai-unsaturated bond of the ketones formed via C3-hydroxylation. Although present in the wild type, the enzymes of the C3-pathway that convert trans-isopiperitenol to menthol isomers are synthetically inactive because of the absence of the key C3-oxygenated intermediate generated by hydroxylation of limonene. These results, which clarify the origins of the C3-and CS-oxygenation patterns, also allow correction of a number of earlier biogenetic proposals for the formation of monoterpenes in Mentha.The monoterpene constituents of the essential oils of peppermint (Mentha piperita L.) and spearmint (native = Mentha spicata L.; Scotch = Mentha x gracilis [28]) are distinguished by the position of oxygenation on the p-menthane ring3 (18,25). Peppermint produces almost exclusively monoterpenes bearing an oxygen function at C3, such as menthone and menthol, whereas spearmint species produce almost exclusively monoterpenes bearing an oxygen function at C6, typi-