| The Scutellaria baicalensis stem-leaf as a non-traditional medicinal part,is very often discarded without further effectively use during processing.Previous studies have documented that S.baicalensis stem-leaf rich in flavonoids possesses a wide range of potential useful medicinal properties,such as antibacterial,anti-inflammatory,and cardiovascular protection etc.Hence,the S.baicalensis stem-leaf is awaiting further development and exploitation for the potential use.Here,the study focuses on the resource utilization of S.baicalensis stem-leaf and involves four parts,literature survey,investigation on optimal harvesting mode of S.baicalensis and assessment of its biomass reserves,analysis and preparation of flavonoids in S.baicalensis stem-leaf,and research on improving the quality and utilization of S.baicalensis stem-leaf using biotransformation technology.Firstly,we established an optimal harvesting mode of S.baicalensis,improving the quality and utilization of S.baicalensis stem-leaf as well as its root.Regarding field experiments,we harvested the stem-leaf 3-5 cm from the ground in late-August and excavated the root in midOctober was suggested to be an optimal harvest model for S.baicalensis(two-year-old or threeyear-old).The yield of S.baicalensis stem-leaf was about(0.66 ± 0.14)kg/m2 and its flavonoid content could reach 67.41 mg/g.Of note,the biomass of S.baicalensis root was unaffected with the total content of four compounds including baicalin increasing by 8.82-23.79%,significantly improving the productivity of S.baicalensis.Secondly,we formulated an efficient and environmentally-friendly preparation method for total flavonoids in the S.baicalensis stem-leaf.Optimal processing was chosen on the basis of univariate analysis and orthogonal test.The results showed that the yield of flavonoid fraction was 9.97%,the yield of flavonoid components was 6.58%,and the yield of isocarthamidin-7-O-β-Dglucuronide,carthamidin-7-O-β-D-glucuronide and scutellarin was 2.60%,1.26%,1.48%,respectively.Moreover,the optimal extraction process was that S.baicalensis stem-leaf was extracted with 12 times of 40%ethanol under heat reflux two times(2×1 h).The best purification process was as follows:the resource loading volume was 8 mL liquid extracted from 8 g S.baicalensis stem-leaf per 10 g HP-20 resin,the ratio of resin column diameter to height was 1:3,elution with 4 bed volume 30%ethanol after the removal of impurities with 4 bed volume distilled water.Finally,we presented a microbial solid-state fermentation strategy for improving the palatability,nutritional and medicinal value of S.baicalensis stem-leaf.As a result,the flavonoid glycosides in S.baicalensis stem-leaf achieved de-glycosylation with Aspergillus niger or its mixture with Bacillus subtilis and Candida utilis.In addition,the optimal fermented condition was that the culture medium with 60%water content was inoculated with 20%A.niger or with 15%mixture(A.niger:B.subtilis:C.utilis=1:1:2)at 35℃ for 9 days.Compared with unfermented stem-leaf,flavonoid aglycones were critical component in fermented stem-leaf.At the same time,the total amino acids content was increased by 135.93%-192.92%.The acid detergent fiber(ADF)and neutral detergent fiber(NDF)contents were decreased by 16.96%-18.82%,34.11%-36.40%,respectively.There was an 8-fold reduce in minimal inhibitory concentration(MIC)and minimum bactericide concentration(MBC)against Escherichia coli.Moreover,fermented stem-leaf significantly enhanced the inhibitory effect on Staphylococcus aureus biofilm formation and reduced mRNA levels of TNF-α and IL-6 mRNA in RAW264.7 cells primed with LPS.Thus,the palatability,nutritional value and medicinal value of S.baicalensis were dramatically promoted following fermentation.In summary,our work could provide the basis for further application of S.baicalensis stemleaf in functional feed additives,thereby facilitating the green health development of its resources and livestock and poultry breeding industry. |
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