Changes in the Amounts and Constituents of Essential Oils during Curcuma Species Growth

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Rhizomes from Curcuma species are widely used as spices, dyes, and medicines. As medicinal constituents in Curcuma species, curcumin and essential oil components (terpenoids) are produced during plant growth. We examined the changes in percentages and constituents of essential oils in the organs of the Curcuma species turmeric and yellow zedoary cultivated in Kochi, Japan during different growth periods. Turmeric had higher aboveground and rhizome dry weights and a lower harvest index than yellow zedoary. In both species, essential oil percentages were significantly greater in rhizomes than in leaves and stems. During the growth period of October to November, essential oil percentages significantly increased in rhizomes and decreased in leaves. Essential oil amounts, calculated as the products of percentage content and dry matter, were greatest at maturity in November as rhizome dry weight and essential oil percentages increased. A chromatographic analysis revealed that turmeric had 22 essential oil constituents comprising more than 1% of the relative area and that ar-turmerone and zingiberene were the major constituents. The ar-turmerone content in rhizomes tended to increase with growth. Yellow zedoary had 21 essential oil constituents, and the major constituent was 1,8-cineole. Essential oil constituents in yellow zedoary were similar between leaves and rhizomes, but were different from those observed in stems. 1,8-Cineole tended to decrease in rhizomes with growth. Thus, the essential oil percentages and constituents were different between species, but these traits also varied in different organs during growth.