The geographical discrimination of Ginger (Zingiber officinale) using HPLC and UV spectroscopy in combination with chemometric analysis

Ginger ( Zingiber officinale Roscoe) is a popular spice used worldwide owing to its pungency and aromaticity. In addition, this rhizome has been traditionally used for its medicinal properties in many countries [1]. The most valuable products of ginger are its volatile oil and oleoresin which are highly affected by many factors including geographical origin and methods of preparation [2]. This fact contributed to its quality control challenge, which prompted this study. Nineteen samples of the rhizomes (in powder and entire forms) were collected from Taiwan (1 sample), China (6), Nigeria (1), India (1), Sri Lanka (2), Thailand (1) as well as 7 commercial samples of unconfirmed origin collected in Egypt. The methanolic extracts were assessed using HPLC where the entire chromatographic profile represented by 59 peaks was subjected to chemometric analysis. The 4 major components that accounted for most of the variance were identified as 6, 8, and 10 gingerol as well as 6-shagoal; repeatedly reported in literature as the main phenolic components of ginger [3]. To compare the samples, different pattern recognition procedures including PCA and HCA were applied. The results were confirmed using UV spectroscopy by applying the same computational software. The clustering pattern of the samples showed a clear demarcation of most of the Chinese samples except for samples Ch5 & 6 with much higher concentrations of 8 and 10-gingerol. The sample from Taiwan appeared as a distinct outlier due to its considerably high concentration of 6-gingerol. The Nigerian samples showed higher concentrations of 6 and 10-gingerol which attributed to its clustering in the top right quadrant in both score plots. The 7 commercial samples were correctly clustered closely to their claimed geographical origins (Com 1, 2 and 3 from China; 4 and 5 from Nigeria; 6 and 7 from India). This simple method can be used to discriminate as well as assert the quality of ginger from different origins. Fig. 1: PCA score plot showing segregation of 19 ginger samples using UV spectroscopy Fig. 2: PCA score plot showing segregation of 19 ginger samples using HPLC