Melilotus alba officinalis

Coumarin was first isolated by Vogel in 1820 by extraction from tonka beans (Dipteryx odorata). It was subsequently identified in a large number of plants belonging to many different families. Its better known occurrences are in sweet clover (Melilotus alba and M. officinalis), sweet woodruff (Asperula odorata), vanilla leaf (Trilisa odoratissima), vanilla beans (Vanillaplanifolia), cassia (Cinnamorum cassia), lavender (Lavendula officinalis) and balsam of Peru (Myroxylon pereirae) (Perone, 1972 Maries et al, 1987 Boisde Meuly, 1993 Budavari, 1998). 

Although free coumarins are known to occur in plants, most simple coumarins occur as glucosides. The involvement of such glucosides in the biosynthetic sequence is a unique feature among higher plants. The -D-glucoside of o-coumarinic acid (7) (Fig. 9.2) is found in plants such as sweet clover (Melilotus alba) and lavender Lavandula officinalis). Usually, free coumarin (1) is formed by hydrolysis of the glucoside and subsequent lactonization of the Z-o-coumarinic acid (8). A similar situation probably is true for umbelliferone and scopoletin (Haslam, 1974). 

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