Supercritical carbon dioxide extraction of eugenol-rich fraction from Ocimum sanctum Linn and a comparative evaluation with other extraction techniques: Process optimization and phytochemical characterization

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Ocimum sanctum Linn., commonly known as Tulsi in India, is pharmacologically important owing to its active constituents, chiefly eugenol. In this work, supercritical carbon dioxide (SC-CO2) extraction has been performed with Krishna tulsi to maximize the yield of eugenol in the extracts and comparatively evaluated against conventional extractions. Phytochemical analyses of chlorophyll-lean and chlorophyll-rich SC-CO2 extracts showed promising results. SC-CO2 extract with maximum eugenol content (4.631mgg−1 dry tulsi powder) was obtained at 70°C, 400bar and 1.5h extracting time. However under these extraction conditions, appreciable amount of cuticular waxes and chlorophyll co-eluted. Eugenol-enriched (4.141mgg−1 dry tulsi powder) chlorophyll-lean extract was obtained at 50°C, 100bar after 1.5h extracting time. Comparative study of phytochemical properties of extracts obtained by several extraction techniques, established that the SC-CO2 extract has the best combination of eugenol and phenolic content along with reducing power, anti-inflammatory, antimicrobial and antioxidant activities. The chlorophyll-rich and chlorophyll-lean extracts of SC-CO2 extracts have comparable phytochemical properties. SC-CO2 extraction has been successfully employed for extraction of eugenol from Krishna tulsi with appreciable nutraceutical potency. We envisage that both chlorophyll-lean and chlorophyll-rich extracts of the same would have promising applications in food and pharmaceuticals.