Effect of Drying on the Composition of Secondary Metabolites in Extracts from Floral Parts of Curcuma longa L.

Background: Curcuma longa is a rhizomatous herbaceous plant of Zingiberaceae family, originating from South Asia and very widespread in hot and rainy regions of the globe. The rhizomes are very popular spice and used as food additives for its coloring, aromatic, food preservation and nutritional properties.

Aim: The aim of this study was to assess the drying effect of floral parts of C. longa at laboratory and incubator temperature (35°C) on the composition of secondary metabolites in general and polyphenolic compounds in particular.

Place and Duration of Study: The study was carried out at the Laboratory of Natural Products, Department of Chemistry, Faculty of Sciences, University of Kinshasa between November 20 and December 10, 2016.

Methodology: Floral parts of C. longa were collected. Petals were collected every day while sepals were collected 20 days after the first petal appeared. The phytochemical screening was used as per the standard protocol and it was assessed between floral parts dried in the laboratory temperature and floral parts dried in the incubator at 35°C.

Results: The findings revealed the presence of total polyphenols, flavonoids, and tannins in petal extracts dried in the incubator at 35°C. However, flavonoids and tannins were not detected in extracts from petals dried in the laboratory temperature. Phytochemical screening findings of the organic phase of C. longa floral parts revealed the presence of free quinones and terpenes in sepal extracts dried in the incubator at 35°C while those of extracts from the same part of the dried plant in the laboratory temperature revealed the presence of terpenes and steroids.

Conclusion: Future studies should carry out a similar study using the spectrophotometry method to determine polyphenolic compounds and confirm our hypothesis on the degradation of polyphenolic compounds during the drying of C. longa floral parts in the laboratory temperature.