Optimisation of patchoulol in the lipid-soluble concentrates of Pogostemon cablin using response surface methodology (RSM) coupled with genetic algorithms (GA)

Abstract

Pogostemon cablin Benth. contains abundance of patchoulol as one of the bioactive components. The present study demonstrated comprehensive optimizations of ultrasonic assisted extraction (UAE) and microwave assisted extraction (MAE) to achieve maximum lipid-soluble extract comprising highest patchoulol content by response surface methodology (RSM) followed by genetic algorithms (GA) approach. The extraction variables such as solute to solvent ratio (UAE, 10–30 g mL−1; MAE, 40–60 g mL−1), time (UAE, 10–20 min; MAE, 30–120 s) and sono-frequency (30–50 kHz) or microwave power (300–900 W) exerted significant influence on the yield and patchoulol content. RSM based optimizations for UAE resulted maximum yield of 182.24 mg/g of plant material consisting 48.84% patchoulol, while, yield 227.46 mg/g of plant material comprising 30.60% patchoulol were recorded under MAE. With the use of GA, the optimized values were further refined to obtain maximum yield of 207.87 mg/g of plant material comprising of 53.45% patchoulol under UAE, whereas, maximum 230.03 mg/g of plant material yield consisting of 31.71% patchoulol was achieved using MAE. UAE and MAE based kinetic modeling studies revealed involvement of more than one extraction mechanisms to achieve maximum yield and patchoulol (%). Further, higher extraction yield using MAE and UAE were also explained from the scanning electron microscopic (SEM) images, showing disintegration of matrix cell wall with numerous fractures leading to better dissolution of phytoconstituents in the extracting medium. Additionally, patchoulol content in the extract was significantly enhanced to 92.70% using silica gel. Patchoulol 92.70% and 53.45% containing extracts displayed excellent fungal mycelial inhibition against virulent strains of Aspergillus flavus (EC50 27.0–29.2 μg mL−1) and A. fumigatus (EC50 41.5–57.2 μg mL−1), respectively.