Triterpenes secondary alcohols

Mostly, terpenoids originate from plants, but they are also synthesized by other organisms, including yeast and bacteria, as primary or secondary metabolites. Terpenoids are S5mthesized from two 5-car-bon building blocks that consist of isoprenoid units [62]. Based on the number of building blocks, terpenoids have been classified into four classes monoterpenes (geraniol, carvone, d-limonene, and perillyl alcohol), diterpenes (retinol and trans-retinoic acid), triterpenes (lupeol, oleanic acid, betulinic acid, and ursolic acid), and tetraterpenes (lutein, a-carotene, yS-carotene, and lycopene) [66]. 

Most of the secondary metaboUtes of green algae consist of terpenes and aromatic derivatives, often associated with the first in meroterpenes. This category of secondary metabolites represents nearly 50% of pubUshed results. Halogenated derivatives are uncommon, representing less than 10% of the structures, which are almost exclusively brominated derivatives. Among sulfur derivatives, some triterpenic alcohols related to cycloartenol have been isolated, of which some are sulfated. 

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