Establishment of HPLC fingerprint, chemical pattern recognition analysis and content determination of aloe vera
Aloe vera is an important edible medicinal herb, belonging to the lily family and the genus Aloe. It is a perennial evergreen fleshy herbaceous plant with a cold nature and a bitter taste. Ancient prescriptions record that it has the effects of clearing liver heat, promoting bowel movements, dispersing nodules, and treating ringworm. There are over 500 varieties of aloe vera, among which Aloe vera (L.) Burm. f. is the most commonly used medicinal variety, and its products are widely used in various fields such as food (including health food), medicine, cosmetics, etc. In recent years, research on aloe vera both domestically and internationally has mainly focused on comparative analysis of varieties, separation and purification, mass spectrometry analysis, content determination, and pharmacological effects. Research has shown that the main active ingredients of aloe vera are anthrone, anthraquinone, and chromone compounds. In addition, there are chemical components such as polysaccharides, glycosides, amino acids, and organic acids, which have antibacterial, anti-inflammatory, anti-tumor, antiviral, and anti allergic activities.

At present, the combination of fingerprint and chemical pattern recognition is an effective method for evaluating the quality of traditional Chinese medicinal materials. Fingerprint spectra mainly focus on the integrity of medicinal materials, establish common patterns, identify common peaks, and objectively and comprehensively reveal the possible types and quantities of active ingredients in medicinal materials; Chemical pattern recognition technology emphasizes the differences between medicinal herbs, and further narrows the range of active ingredients in medicinal herbs by integrating and correcting fingerprint data information; The combination of the two can achieve the process of overall description and individual analysis of medicinal materials, which can more accurately and objectively reflect the quality differences of traditional Chinese medicine. The main medicinal ingredients of aloe vera medicinal materials are compounds such as aloin and aloe emodin, but the effective ingredients and their contents vary with factors such as the place of origin, growth environment, soil, and harvesting season, which poses certain difficulties in evaluating the quality and safety of aloe vera medicinal materials. In addition, the content determination items for aloe vera medicinal materials in the Chinese Pharmacopoeia (2020 edition) are based on the content of aloin, and the indicator components are single, making it difficult to control the quality of the medicinal materials. Therefore, it is essential to conduct fingerprint and combined chemical pattern recognition research on aloe vera medicinal materials before producing and developing related preparations.

This study used high-performance liquid chromatography (HPLC) to establish fingerprint spectra of 12 batches of aloe vera medicinal materials from different origins, and combined similarity analysis, cluster analysis, principal component analysis (PCA), and orthogonal partial least squares discriminant analysis (OPLS-DA) to study their chemical composition characteristics. The markers that could affect the quality differences of the medicinal materials were screened, and the contents of six markers (aloin D, aloin A, aloin B, 7-O-methyl aloin A, aloin, and aloe emodin) in the 12 batches of aloe vera medicinal materials were determined using the same method. The aim is to ensure the quality of the medicinal materials from the production source and provide scientific basis for quality control and standard improvement of aloe vera medicinal materials. The representative results are as follows.

This study compared the effects of hot reflux method and ultrasound method on the extraction rate of characteristic chromatographic peaks. The results showed that ultrasonic treatment had high extraction efficiency, short time, low loss, and easy operation. At the same time, the effects of extraction solvents (methanol, ethanol) and concentration, extraction time, and liquid to material ratio on the extraction rate of six indicator components in aloe vera medicinal materials were investigated. The results showed that ultrasonic extraction for 20 minutes with 75 mL of 50% methanol aqueous solution was the best. We investigated mobile phase systems such as acetonitrile formic acid aqueous solution, acetonitrile phosphoric acid aqueous solution, and methanol phosphoric acid water. The results showed that when gradient elution was performed using methanol acetonitrile 0.3% phosphoric acid aqueous solution as the mobile phase, the peak shapes of each indicator component were symmetrical, the separation degree was good, the running time was short, and the effect was the best. The peak shapes and resolutions of various chromatographic peaks at different detection wavelengths (254, 280, 310, 330, 360 nm) were compared. The results showed that the absorption intensity of six indicator components at 254 nm was high, the baseline was stable, and the resolution was good. Therefore, 254 nm was selected as the detection wavelength.
The fingerprint spectra of 12 batches of aloe vera medicinal materials identified a total of 23 common peaks. From the similarity results, it can be seen that except for the similarity of less than 0.5 in the Guangxi production area, all others are greater than 0.93, indicating that the chemical composition types and contents of aloe vera medicinal materials sold in the market vary greatly due to different production areas. According to the clustering analysis results, the 12 batches of aloe vera medicinal materials are clustered into 3 categories, which is consistent with the principal component analysis results. Five chromatographic peaks affecting the quality differences of aloe vera medicinal materials were screened using orthogonal partial least squares discriminant analysis, and their contents were determined using the same HPLC method. As aloe emodin is also one of the main bioactive compounds in aloe vera medicinal materials, it is also included as an indicator component in the content determination. The analysis results show that there are significant differences in the content of the six indicator components. This difference may be due to various factors such as geographical environment, climate conditions, harvesting period, soil and field management, planting mode, etc., which affect the accumulation of secondary metabolites in medicinal materials, leading to differences in similarity and content of medicinal materials; Secondly, aloe vera medicinal materials are presented in the form of concentrated substances, and their concentration method, drying process, and sampling location can also cause significant differences in the chemical composition of the medicinal materials.

This study analyzed the differences in the composition of aloe vera medicinal materials from different origins using quantitative fingerprint spectroscopy combined with chemical pattern multivariate discrimination method, and determined the content of six indicator components. This can intuitively evaluate the consistency of aloe vera medicinal materials quality in various origins, and also reflect the differences in chemical composition, providing scientific reference for the quality control of aloe vera medicinal materials and the development of related products in the future.