Study: Microwave Extraction Method Maximizes Antioxidants and CBD From Cannabis Leaves

Researchers from Kasetsart University and the University of the Thai Chamber of Commerce in Thailand used response surface methodology and a Box-Behnken design to optimize MAE conditions. The goal was to extract the highest levels of total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity, and CBD using only water as a solvent—marking a sustainable and environmentally friendly approach. The study tested multiple combinations of temperature (90°C to 150°C), extraction time (10 to 30 minutes), and solid-to-solvent ratio (1:10 to 1:30 g/ml). The optimal extraction conditions were determined to be a solid-to-solvent ratio of 1:28.5 g/ml, a temperature of 150°C, and an extraction time of 23 minutes.

Under these conditions, the cannabis leaf extract yielded 19.08 mg GAE/g dw TPC, 8.98 mg QE/g dw TFC, 42.09 mg Trolox/g dw in FRAP antioxidant capacity, and 44.14 mg Trolox/g dw in ABTS activity.

Notably, the study found that the antioxidant values for CBD were highly correlated with its phenolic composition. FRAP values had a particularly strong correlation with CBD content (r = 0.914), indicating that CBD may contribute significantly to the plant’s antioxidant profile.

This research highlights the growing potential of cannabis leaves—typically an underutilized part of the plant—as a sustainable source of bioactive compounds. The findings could help guide the development of functional food products, nutraceuticals, and cosmetics using green extraction methods.

The study’s conclusion section states:

The application of MAE significantly enhances the extraction yields of phytochemicals and antioxidant activities from Cannabis leaves, making them a valuable source of bioactive compounds, particularly antioxidants. The main effect experiments revealed that the SSR was the most significant factor influencing phytochemical and antioxidant yields, followed by temperature and extraction time. A higher SSR resulted in increased extraction of phytochemicals and antioxidant activities. Increasing the temperature positively influenced antioxidant activities and CBD content, while extraction time had a less significant impact on these parameters. Optimization of the extraction conditions, with an SSR of 1:28.5 g-dried Cannabis leaves/ml water, a temperature of 150°C, and an extraction time of 23 min, yielded high levels of phytochemicals (TPC of 19.08 ± 0.50 mg GAE/g dw and TFC of 8.98 ± 0.30 mg QE/g dw) and antioxidant activities (FRAP of 42.09 ± 0.55 mg Trolox/g dw and ABTS activity of 44.14 ± 0.39 mg Trolox/g dw). These findings emphasize the potential of these optimized conditions as an environmentally friendly and efficient method for producing functional ingredients suitable for use in the food industry.