The effect of different drying methods on the chemical composition and antioxidant activity of Acacia flower medicinal materials
Acacia flowers are the dried inflorescences or buds of the legume Albizia julibrissin Durazz. The former is called “Acacia flowers”, while the latter is called “Acacia rice”. They are sweet and flat in nature, and have a calming effect on the heart and liver meridians, with the ability to relieve depression and soothe the mind. Hehuan flower has a long history of medicinal use, first recorded in the “Shennong Bencao Jing”. Throughout history, there have been records of the use of this herb to relieve depression and soothe the mind. Modern research has shown that Acacia flowers contain a large amount of flavonoids such as quercetin and quercetin, as well as a small amount of active ingredients such as polysaccharides and volatile oils. They have various pharmacological effects such as antidepressant, sedative hypnotic, anti anxiety, hepatoprotective, and antioxidant.

Acacia flowers contain a large amount of flavonoid glycosides, which are easily hydrolyzed by enzymes. Traditional Chinese medicine containing glycosides often also contains enzymes that can hydrolyze the glycosides. Drying is a necessary initial processing process for fresh Acacia flowers after harvesting in the production area. Different drying and initial processing processes may activate or inhibit enzyme activity, leading to hydrolysis or preservation of active substances under the action of enzymes, thereby causing changes in the quality of Acacia flower medicinal materials. ‘Qingqing’ is a method of extinguishing fire by using certain enzymes in the harvested plant body. The “withering” method is widely used in the initial processing of Chinese medicinal materials. Suitable “withering” methods can destroy the enzyme activity in fresh plants, which is beneficial for preserving active substances and affecting the characteristics and quality of medicinal materials. A reasonable drying and initial processing method plays an important role in the retention of flavonoid glycosides in Acacia flowers. The traditional drying method for Acacia flowers is sun drying, which is greatly affected by the natural environment. The appearance and morphology of Acacia flowers of different specifications vary greatly. It is unclear whether the universal sun drying method for Acacia flowers and Acacia rice is suitable.

Therefore, this study takes Acacia flowers and Acacia rice as the research objects, compares the effects of traditional drying methods (sun drying, shade drying), different withering and drying methods (steam withering and drying, microwave withering and drying), drying (30, 50, 70, 90 ℃), and freeze-drying methods on the key active substances and antioxidant activity in two specifications of Acacia flowers, and provides scientific basis for the processing and utilization of Acacia flowers in the production area.

 

This article studies the effects of traditional drying methods (sun drying, shade drying), withering drying methods (steam withering after drying, microwave withering after drying), drying (30, 50, 70, 90 ℃), and freeze-drying on the quality of two specifications of Acacia flowers. Establish an HPLC method to determine the content of isoquercitrin, quercitrin, and quercetin, and use UV visible spectrophotometry to determine the total flavonoid content. Compare the differences in flavonoid content of Acacia flowers treated with different drying methods. There is a significant difference in the content of flavonoids in Acacia flowers treated with different drying methods. Compared with traditional drying methods, the total flavonoid content, isoquercitrin, and quercitrin content of dried Acacia flowers after steam withering were significantly higher, while the quercetin content was lower. The total flavonoids and isoquercitrin content were significantly highest in the freeze-dried Acacia rice samples, and the quercitrin content was significantly highest in the steam killed and dried samples. The appropriate “withering” method can destroy the enzyme activity in fresh plants and retain active substances. At this time, the steam withering method with strong permeability can destroy the cell structure and inhibit the activity of hydrolytic enzymes, reducing the hydrolysis of flavonoid glycosides; During the freeze-drying process, water can be directly sublimated from the solid state to the gaseous state for removal. Low temperature drying can inhibit the activity of hydrolytic enzymes and also facilitate the preservation of active ingredients.
The flavonoid components isoquercitrin, quercitrin, and quercetin in the flowers of Acacia are the main active ingredients in two medicinal materials of Acacia, which have significant antioxidant effects. This article uses five antioxidant methods to evaluate the quality of Acacia flower medicinal materials and their antioxidant activity against different free radicals. Due to the different experimental principles of the five selected antioxidant methods, the antioxidant activity of the two Acacia flower medicinal materials can be objectively comprehensively evaluated. The experimental results showed that there were significant differences in the antioxidant activity of samples of Acacia flowers treated with different drying methods. Further correlation analysis showed that quercetin was significantly positively correlated with DPPH free radical scavenging ability, Fe3+reduction ability, and total antioxidant capacity (P<0.05). ABTS free radical scavenging ability was highly significantly positively correlated with total flavonoid content (P<0.01), and quercetin content was significantly positively correlated with ABTS free radical scavenging ability (P<0.05). The total flavonoid content and quercetin content were significantly positively correlated, and quercetin content could be used as an evaluation index of total flavonoid content. It is speculated that quercetin and quercetin are the main antioxidant active substances in two Acacia flower medicinal materials.
Different drying treatments have significant differences in the chemical composition and antioxidant activity of Acacia flowers. PCA analysis was used to comprehensively evaluate the effects of different drying methods on the quality of Acacia flowers and Acacia rice based on indicators such as quercetin, quercetin, isoquercetin, total flavonoid content, Fe3+reduction ability, DPPH free radical scavenging ability, ABTS free radical scavenging ability, O2- free radical scavenging ability, and total antioxidant capacity. Different specifications of samples were significantly affected by drying methods. The comprehensive evaluation found that both Acacia flowers and Acacia rice should not be dried in the shade, as the drying time was longer and may cause damage to the moldy quality of the samples. Acacia flowers were suitable for drying at 70 ℃, while Acacia rice was suitable for freeze-drying. This study provides reference for the rational selection of initial processing methods and improvement of quality control standards for two Acacia flower medicinal materials.