The current issues of standardization of Aloe arborescens Mill. leaves

BACKGROUND: Aloe arborescens Mill. leaves contain a whole complex of biologically active compounds (derivatives of anthraquinone, anthrone, pyrone, biopolymers, etc.) and are widely used in medical practice as raw materials for the production of anti-inflammatory, wound healing agents. The presence of anthracene derivatives in the leaves determines the laxative activity of raw plant materials and preparations. It emphasizes the importance of Aloe arborescens preparations for internal use in inflammatory diseases accompanied by constipation and decrease in secretory activity. Another biologically active compound with which the anti-inflammatory activity of aloe leaves may be associated with a pyrone derivative aloenin. At the same time, despite the widespread use in medicine and a well-studied chemical composition, the problems in the field of standardization of raw materials and preparations of Aloe arborescens are still urgent. The methods for determining the quantitative content of anthracene derivatives described in the literature are multistage, they provide for preliminary acid hydrolysis in combination with oxidation, liquid-liquid extraction of the formed aglycones and complexation with magnesium acetate. The approved regulatory documents for aloe raw materials and preparations does not provide for the assay of aloenin

AIM: The aim is to develop the methods for determining the quantitative content of biologically active compounds in the raw materials and preparations of fresh leaves of Aloe arborescens by using the spectrophotometric method and the high-performance liquid chromatography method.

MATERIALS AND METHODS: The objects of research were fresh leaves of Aloe arborescens Mill., and juice obtained ex tempore from fresh leaves of aloe. Samples of raw materials were collected in the summer and autumn of 2020 in the Winter Garden of the Department of Pharmacognosy with Botany and Bases of Phytotherapy at Samara State Medical University. Individual substances were isolated by column chromatography. In the study, the Bruker DRX 500 instrument (126.76 MHz) was used to determine ¹³C NMR spectra, and the Bruker AM 300 instrument (300 MHz) was used to determine ¹H NMR spectra. Mass spectra were recorded on mass spectrometer Kratos MS-30, UV spectra were recorded by means of the spectrophotometer Specord 40 (Analytik Jena). High-performance liquid chromatography analysis was carried out with the use of the chromatograph Milichrom-6 (Nauchpribor, Russia).

RESULTS: As a result of the study, aloenin and a mixture of aloins A and B (barbaloin) were isolated from the leaves of Aloe arborescens by with the use of column chromatography. The method for the determination of the quantitative content of aloenin by microcolumn reversed-phase high-performance liquid chromatography with UV detection (306 nm) was developed, the mobile phase was acetonitrile: 1% acetic acid solution in water in the ratio of 25:75, the elution rate is 100 μL / min. The method for the quantitative determination of the total amount of anthracene derivatives in Aloe arborescens fresh leaves (differential spectrophotometry with an alkaline-ammonia solution at 412 nm) was developed. The optimal conditions for the extraction were selected. They are extractant of 40% ethyl alcohol, extraction within 60 minutes at the ratio of “raw material – extractant” is 1:50. Validation analysis has shown that the developed methods are characterized by satisfactory metrological indicators.

CONCLUSIONS: The obtained results can be used to update the pharmacopoeial monograph “Aloe arborescens leaves fresh”.