Early harvest of leaves affects curcumin content and essential oils yield in turmeric (Curcuma longa L.)

Curcuma longa L. is highly regarded for its content of curcumin and essential oils, both of which hold considerable medicinal and commercial significance. Although the rhizome is the primary source of curcumin, the leaves also contain essential oils that can increase the overall economic value of the plant. The presence of essential oils in the leaves can add commercial value to the crop, as these oils can be used in the pharmaceutical, perfumery and cosmetic industries. The present study reports the effect of early harvesting of leaves, one month before full maturity of the crop, on the curcumin content and essential oil yield from younger leaves and mature post-harvest waste leaves. It was observed that essential oil content decreased in the matured-dried leaves as compared to that of the younger leaves collected at one month before rhizome harvest. The magnitude of decreased of essential oils yield in dried-mature leaves as compared to younger leaves was 62.59 % in Rajendra Sonia, 74 % in Morangia, 19.75 % in IISR-Roma, 2 % in IISR-Pratibha, 0.61 % in IISR-Alleppy Supreme and 18.30 % in Megha Turmeric-I. Although in the variety IISR-Alleppy Supreme and Megha Turmeric-I, there was an observed decrease in EO yield in the matured-dried leaves as compared to younger leaves but the changes were not significant. The curcumin content was differentially affected by the time of leaf collection, which is also cultivar dependent. Collection of leaves at one-month before rhizome harvest, curcumin content was decreased in the variety Roma by 39.21 %, Morangia by 9.2 % and Rajendra Sonia by 8.0 %, while in other varieties like IISR-Pratibha, IISR-Alleppy Supreme and Megha Turmeric-1, the curcumin content increased by 7.33 %, 3.48 % and 6.45 %, respectively. Essential oils from both stages of leaves were shown to have comparable reducing power and antioxidant properties. These findings suggest that early collection of leaves at one month before maturity of the rhizome increased the yield of the essential oil content with minimal effect on the curcumin.