Growth years and post-harvest processing methods have critical roles on the contents of medicinal active ingredients of Scutellaria baicalensis

Abstract

Optimizing the processing technology is an effective way to improve the yield of active ingredients for the industrial production of medicinal crops. Baikal Skullcap (Scutellaria baicalensis Georgi) is a perennial herb in the Lamiaceae family and its dried root is used as a famous traditional Chinese medicine (TCM). Modern pharmacological studies have shown that the active ingredients of S. baicalensis have important pharmacological effects including anti-oxidation, anti-bacterial, anti-viral, anti-tumor, and anti-inflammation. Specifically, it is recently found that S. baicalensis has significant curative effects on the treatment of corona virus disease 2019 (COVID-19). In recent years, the market demand for the medicinal products of S. baicalensis is increasing because of its great medicinal values. However, the annual yield of active ingredients originated from the root of S. baicalensis is limited due to that little progress has been made on the traditional processing technology used in the extraction process. A pressing issue faced by both herbalists and scientists is how to improve the processing efficiency, thereby obtaining the maximum yield of products for S. baicalensis. In this study, a systematic analysis on the effects of growth years and post-harvest processing on the contents of medicinal active ingredients of S. baicalensis was conducted. The contents of eight active ingredients (baicalin, wogonoside, baicalein, wogonin, scutellarin, scutellarein, apigenin, and chrysin) in roots of S. baicalensis of different growth years (ranging from 1 year to 15 years) were estimated using high performance liquid chromatography (HPLC) and further analyzed to determine the optimal harvest period. In particular, the contents of six active ingredients in different parts (cortex and stele) of the root of S. baicalensis were estimated and compared. Meanwhile, the dynamic changes of the contents of active ingredients in fresh-crush and fresh-cut roots of S. baicalensis at room temperature were compared and analyzed to reveal the influence of post-harvest treatment on the contents of active ingredients. In addition, the effects of six different post-harvest treatments on the contents of active ingredients were systematically designed and compared to determine the best primary processing technology. The results showed that the best harvesting period for S. baicalensis should be determined as 2-3 years based on comprehensive evaluation of active ingredient content, annual yield increment, and land use efficiency. The contents of active ingredients including baicalin, wogonoside, baicalein, and wogonin in cortex were significantly higher than those in stele (P ≤ 0.05). The contents of baicalin, wogonoside, and scutellarin in fresh roots of S. baicalensis significantly reduced as the storage time increased, but the reduction of fresh-cutting was significantly lower than that of fresh-crushing. For the effects of different processing treatments, the contents of four main active ingredients (baicalin, wogonoside, baicalein, and wogonin) under drying (D) and cutting-drying (C-D) treatments were significantly higher than those of the other four treatments (P ≤ 0.05). Collectively, the above results will not only provide novel processing methods that will improve the yield of active ingredients for S. baicalensis, but also shed light on the optimization of processing technology for the industrial production of medicinal crops.

Keywords: Active ingredient; Growth year; Industrial production; Post-harvest; Processing method; Scutellaria baicalensis.

Graphical abstract

Fig. 1

The plant and main medicinal material of S. baicalensis used in pharmaceutical industry. (A) The plant of S. baicalensis. From left to right: whole plant, leaf, stem, flower, and root; (B) The roots of S. baicalensis with different growth years. From left to right: 0.5, 1, 2, 3, 4, 5, 7, 9, 12, 15; (C) The different parts of roots from 2-year-old S. baicalensis. From left to right: whole root, root slice, cortex, stele; (D) The annual demand and yield of medicinal products of S. baicalensis used in pharmaceutical industry in China. Data were collected and analyzed by our group. Unit: tons.

Fig. 2

The flavonoid biosynthesis in roots of S. baicalensis. (A) The flavonoid biosynthesis in S. baicalensis. PAL: phenylalanine ammonia lyase; 4CL: 4-coumarate CoA ligase; CHS: chalcone synthase; CHI: chalcone isomerase; FNSI: flavone synthase I; FNSII: flavone synthase II; F6H: flavone 6-hydroxylase. (B) The roots of S. baicalensis.

Fig. 3

The HPLC chromatograms of eight active ingredients in roots of S. baicalensis. (A) The chromatograms of standards of eight active ingredients. 1: scutellarin; 2: scutellarein; 3: baicalin; 4: wogonoside; 5: apigenin; 6: baicalein; 7: wogonin; 8: chrysin. (B) The representative chromatograms of eight active ingredients of root sample from 2-year-old S. baicalensis. 1: scutellarin; 2: scutellarein; 3: baicalin; 4: wogonoside; 5: apigenin; 6: baicalein; 7: wogonin; 8: chrysin.

Fig. 4

The HPLC standard curves of eight active ingredients in roots of S. baicalensis. The HPLC standard curves of eight active ingredients in roots of S. baicalensis were calculated using linear regression. (A) baicalin; (B) scutellarin; (C) chrysin; (D) scutellarein; (E) wogonoside; (F) apigenin; (G) wogonin; (H) baicalein.

Fig. 5

The contents of six active ingredients in whole root, cortex and stele of S. baicalensis. The contents of six active ingredients (from A to E: baicalin, wogonoside, scutellarin, baicalein, wogonin, and scutellarein) in whole root, cortex and stele of 2-year-old and 15-year-old S. baicalensis were estimated and compared. Data were presented as Mean ± SD. *P ≤  0.05, **P ≤  0.01 (Student’s t test).

Fig. 6

The contents of eight active ingredients in fresh-crushed roots of S. baicalensis with different storage time. The contents of eight active ingredients in fresh-crushed roots of S. baicalensis with different storage time (0 h, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 6 h, 8 h, 11 h, 22 h, 23 h, 24 h, and 25 h) were estimated and compared. (A) baicalin and baicalein; (B) wogonoside and wogonin; (C) scutellarin and scutellarein; (D) apigenin; (E) chrysin. Data were presented as Mean ± SD.

Fig. 7

The contents of eight active ingredients in fresh-cut roots of S. baicalensis with different storage time. The contents of eight active ingredients in fresh-cut roots of S. baicalensis with different storage time (0 h, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 6 h, 8 h, 11 h, 22 h, 23 h, 24 h, and 25 h) were estimated and compared. (A) baicalin and baicalein; (B) wogonoside and wogonin; (C) scutellarin and scutellarein; (D) apigenin; (E) chrysin. Data were presented as Mean ± SD.

Fig. 8

The correlation analysis of medicinal active ingredients in fresh-crushed roots of S. baicalensis. The correlations among eight active ingredients in fresh-crushed roots of S. baicalensis were analyzed. (A) The correlation of the contents between baicalin and baicalein; (B) The correlation of the contents between wogonoside and wogonin; (C) The correlation of the contents between scutellarin and scutellarein. Data were presented as Mean ± SD.

Fig. 9

The total content of four main active ingredients in roots of S. baicalensis under different treatments. The total content of four main active ingredients (baicalin, wogonoside, baicalein, and wogonin) in roots of S. baicalensis under different treatments were estimated and analyzed. D: drying; S: steaming; C: slicing. Different letters indicate significant differences of the total content of four main active ingredients among different treatments (P ≤  0.05). Data were presented as Mean ± SD.