Raman spectroscopy: A rapid, non invasive tool for determining carotenoids in inflorescences of Tagetes erecta L

Determination of carotenoids in Tagetes erecta L. is basic in researching this plant for industrial purposes, with the aim of obtaining varieties with high-carontenoid content in the inflorescences. The classic chemical analysis, however, is slow and costly. Using inflorescences of four T. erecta L. varieties: white, cream-colored, yellow and orange, RAMAN spectroscopy was applied to fresh ligules (LF) and to ligule powder (HL), while chemical analysis was performed on dry ligules to determine the total xantophyll concentration. With the first method, adimensional intensity of 4.93082, 8.78653, 17.9756, 53.40643 (LF) and 42.84.53.52, 219 and 467.65 (HL) was recorded in the RAMAN 1524 cm^-1 band. With the second method, the total concentrations of xanthophylls in HL were 0.40678, 1.03446, 3.46356 and 8.15977 g kg^-1. The order of the values corresponds to the white, cream-colored, yellow and orange varieties; the relationship was verified with exponential models. By relating the RAMAN values with total xanthophylls in the powder samples by exponential models, a linear correlation (R=0.97) was found between the results of the two methods of quantitative determination of carotenoids, making the use of RAMAN favorable as a rapid and inexpensive technique.