Green Extraction of Phenolic Compounds from Orthosiphon stamineus Using Deep Eutectic Solvents and Non-Conventional Techniques
Yoke Shan Wong1*, Angky Wahyu Putranto2, Ngoh Gek Cheng1, Rozita Yusoff1

1. Sustainable Process Engineering Centre, Department of Chemical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
*Email: yokeshann[at]gmail.com
2. Department of Biosystems Engineering, Faculty of Agricultural Technology, Universitas Brawijaya, Malang, East Java, 65154, Indonesia

Abstract

Growing consumer awareness of health and wellness, along with a preference for natural and sustainable products, has driven the use of plant extracts in cosmetics, pharmaceuticals, and food industries. Orthosiphon stamineus (Misai Kucing), a Southeast Asian herb, is valued in traditional medicine for its phenolic compounds (PCs) and associated health benefits. In line with green chemistry principles, deep eutectic solvents (DES) are emerging as eco-friendly alternatives for extracting these bioactive compounds. This study develops a sustainable extraction strategy for PCs from Misai Kucing using non-conventional methods including ultrasound-assisted (UAE), microwave-assisted (MAE), and pulsed electric field (PEF) extraction. Two DESs (choline chloride-ethylene glycol, acidic- and choline chloride-urea, alkaline) were tested against water as a neutral control. This study examines how solvent pH and viscosity influence extraction, compares sequential versus single-step extractions, and evaluates the antioxidant activity and toxicity of DES-extracted PCs. Results showed marked differences among techniques and solvents. DESs outperformed water, with choline chloride-ethylene glycol combined with MAE achieving the highest yields. Sequential extraction generally improved PC recovery and antioxidant activity. Moreover, DES-based extracts exhibited lower toxicity than those obtained with conventional solvents like ethanol. The findings demonstrate the potential of DESs coupled with advanced extraction methods to efficiently recover phenolic compounds from O. stamineus. The optimized strategies provide a greener, more effective approach, supporting broader applications of natural extracts across industries.

Keywords: Phenolic compounds- Green extraction- Deep eutectic solvent- Misai kucing- Toxicity

Topic: Agricultural and bioprocess engineering