Administration of labeled compounds such as [10-³H]-10-hydroxygeraniol (8), [10-³H]-and [11-³H₂]-iridodial (7), [10-³H]-and [11-³H₂]-iridodial glucoside (9) to Lamium amplexicaule, Deutzia crenata and Galium spurium var. echinospermon established that lamioside (1), deutzioside (2), scabroside (3), ipolamiide (4), lamiide (5) and asperuloside (6) are biosynthesized in these plants via 10-hydroxygeraniol (8) and iridodial (7).