Rapid discrimination of Eurycoma longifolia extracts by Fourier transform infrared spectroscopy and two dimensional correlation infrared spectroscopy

Eurycoma longifolia is a herbal medicinal plant of South-East Asian origin, popularly recognized as 'Tongkat Ali'. The root extracts have been used in indigenous traditional medicines for its unique antimalarial, anti-pyretic, antiulcer, cytotoxic and aphrodisiac properties. It is an important task that fast and effective analysis methods monitor the inherent qualities of traditional herbal medicines and its corresponding extracts products as a complicated mixture system. Owing to the unique fingerprint character and extensive applicability to test sample, infrared spectral method have been used in many research fields. In this paper, we use FT-IR, second derivative infrared spectroscopy and two-dimensional correlation infrared spectroscopy (2D-IR) step by step to analyze E. longifolia and its different extracts (extracted by hexane, ethyl acetate, dichloromethane and methanol in turn). The findings indicated that FT-IR and 2D-IR can provide many holistic variation rules of chemical constituents. The structural information of the samples indicated that E. longifolia and its extracts contain a large amount of quassinoids, since some characteristic absorption peaks of quassinoids, such as ∼1700 cm−1, ∼1670 cm−1, ∼1600 cm−1,∼1500 cm−1, and ∼1270 cm−1 can be detected. This method, having its high resolution and excellent macroscopic fingerprint features, can not only supply lots of structural information of main components in the complicated system, but also can differentiate the tiny differences between the similar systems according to the macro-fringerprint characters. This method is highly rapid, effective, accurate and well repetitive for pharmaceutical research.