The green and efficient extraction of bioactive compounds from plant biomass is an important area of interest in the pharmaceutical industries. Hydrophilic deep eutectic solvents (DESs) have been considered as green alternatives to conventional solvents for bioactive compound extraction. In this study, we aimed to provide a practical example demonstrating the tunability of hydrophobic DESs as designer solvents to efficiently extract bioactive compounds from plant biomass. Artemisinin, known as the only drug effective in the treatment of malaria, was chosen for extraction from Artemisia annua leaves. A hydrophobic DES named N81Cl-NBA that was tailor-made from methyl trioctyl ammonium chloride and 1-butanol at a molar ratio of 1:4 showed the highest extraction yield. With N81Cl-NBA-based ultrasound-assisted extraction (UAE), the main factors affecting the extraction yield were statistically optimized using a central composite design combined with a response surface methodology. The optimal conditions were obtained as follows: solvent/solid ratio 17.5:1, ultrasonic power 180 W, temperature 45 °C, particle size 80 mesh, and extraction time 70 min. Under these conditions, an extraction yield of 7.9936 ± 0.0364 mg/g was obtained, which was distinctly higher than that obtained using the conventional organic solvent petroleum ether. Moreover, the recovery of the target artemisinin from the N81Cl-NBA extraction solution was achieved by AB-8 macroporous resin with a recovery yield of 85.65%. N81Cl-NBA could be reused at least two times without a significant decrease in extraction yield. This study suggests that not only hydrophilic DESs but also hydrophobic DESs are truly designer solvents that can be used as green and safe extraction solvents for pharmaceutical applications.

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This paper presents a prefermentation treatment method involving fungi to improve flavonoid extraction from the leaves of Ginkgo biloba . The fungi employed for this treatment were screened from the soil present under an ancient ginkgo tree. Seventy-six strains belonging to 23 genera were isolated and identified by a molecular identification method employing 18S rDNA sequences. Thirty-three strains grew well using ginkgo leaves as the growth medium. One strain, Gyx086, with higher extracted yield of flavonoids and more similar to the control, was finally selected for prefermentation processing. The major fermentation factors were optimized by response surface methodology. The optimal conditions for the highest total falvonoid yield were 27.8 °C for temperature, 64.2% for moisture content, and 61 h for fermentation time. Under the optimal condition, a actual total flavonoid yield of 27.59 ± 0.52 mg/g dry weight culture sample was obtained, which was about 70% higher than that of unfermented gingko leaf samples.

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The Moringa oleifera leaf is an important source worldwide with a high nutritional value and functions in food and feed that may also treat a myriad of ailments but the leaf has low organoleptic properties and digestibility. To overcome this shortcoming, a novel Aspergillus niger was isolated from the Moringa leaf material. The fungal strain grows well on moist Moringa leaves and requires no additives. After performing a single factor test for temperature, moisture, inoculation size, and fermentation, the optimized condition was determined by using a response surface method, followed by a small-scale production test. The pleasant, sweet smelling aroma in the fermented leaves was then generated, supplementing than its native repulsive smell. The protein content and digestibility of the leaves increased by 23.4 % and 54.4 %, respectively; the direct-fed microbes reached up to 1.99 × 109 CFU per gram of fermented freeze-dried Moringa leaves. Digestive lignocellulolytic enzymes were substantially produced with 2.97 ± 0.24 U.g−1 of filter paper activity and 564.9 ± 37.4 U.g−1 of xylanase activity. Moreover, some functional components, such as flavonoids and γ-Aminobutyric acid content, were also significantly increased compared to that of the unfermented leaves. In conclusion, the feed quality and digestibility of Moringa oleifera leaves were greatly improved via solid-state fermentation by Aspergillus niger. Fermented Moringa oleifera can be used as a potentially high- quality feed alternative for the animal industry.

To improve the quality of Ginkgo biloba leaves as biological feed additives, twelve Aspergillus niger strains were evaluated for their growth in the moisture ginkgo leaf meal media through solid-state fermentation. The results relating to flavor, flavonoids, enzymes, crude protein, and reducing sugars showed A. niger Gyx086 strain was capable of efficiently fermenting ginkgo leaves. The optimal cultural conditions were three loops of spores inoculation to every 75 g medium containing 60 % water, grew at 28˚C for 48 h. The Gyx086 grew well in the medium. The fermented leaves generated a strong sweet-smelling odor, could be identified by electronic nose equipment using a cluster analysis, other than the original offensive smell from non-fermented ginkgo leaves. Each gram dried culture with Gyx086 showed 2.83 × 109 CFU of A. niger; 3.19 ± 0.37 FPU of acid-resistant filter paper activity. Its total contents of flavonoids, reducing sugars, and crude proteins were 19.95 ± 0.23 mg, 24.28 ± 2.35 mg, and 162.81 ± 3.46 mg in each gram of leaves, 26.03 %, 62.73 %, and 14.58 % higher than the controls, respectively. The essential amino acids and total amino acids contents were 96.41 % and 16.49 % higher than the controls.

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