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Properties of medicinal plants related to NIR spectroscopy

Medical plants as a source of bioactive components are investigated as medicinal plant extracts. A range of spectrophotometric, conductivity, near infrared spectroscopy and chemometric analyses were undertaken as a mean of determining the bioactive quality of 6 widely spread medicinal plant extracts from botanically distinct origins (Lemon balm, Sage, Lavender, Garden Thyme, St. John's wort and Marigold). Spectrophotometric determination of polyphenols and antioxidant capacity was performed. To determine the antioxidant capacity, two methods were used, the broadly used DPPH method and the Briggs- Rauscher method. BR method is performed at pH 2, which is similar to that of the fluids of the main digestive process (human stomach), giving in vitro information on antioxidant activity under "real digestion conditions". Conductivity and total dissolved solids and a NIR spectrum (NIRs) record for each medical plant extract were recorded. Chemometric techniques were used to establish the relationship between a technological method, as NIR spectroscopy, that was coupled with all determined, analytical parameters (total phenols, antioxidant capacity, conductivity and TDS). Partial least squares regression (PLSR) was used to evaluate the relationship between NIRs and bioactive and conductivity properties of medical plants to be able to predict the properties based on the NIR spectra of the medical plant extracts. The results showed high correlation confirming the suitability of NIR analysis for determination and quantification (RPD>3) of polyphenols, antioxidant capacity, conductivity and TDS in medicinal plant extracts.

medicinal plants; antioxidant capacity; NIR spectroscopy

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