Temperature and pH Stability of Anthraquinones from Native Aloe vera Gel, Spray-Dried and Freeze-Dried Aloe vera Powders during Storage

Abstract

The present study explored the stability of extracted anthraquinones (aloin, aloe-emodin and rhein) from whole-leaf Aloe vera gel (WLAG), its freeze-dried powder (FDP) and spray-dried powder (SDP) under varying pH and temperature conditions during storage. Each anthraquinone behaved differently under different processing parameters. The amount of anthraquinones present in the gel was higher than in FDP and SDP. The aloin contents decreased by more than 50% at 50 °C and 70 °C, while at 25 °C and 4 °C, the decrease was moderate. A substantial reduction in aloin concentration was noticed at pH 6.7, whereas it remained unaffected at pH 3.5. The temperature and pH had no significant effect on the stability of aloe-emodin. Interestingly, a small quantity of rhein was detected during storage due to the oxidative degradation of aloin into aloe-emodin and rhein. These findings can provide significant insight into retaining anthraquinones during processing while developing functional foods and nutraceuticals to obtain maximum health benefits.

Ultrasound-Assisted Encapsulation of Anthraquinones Extracted from Aloe-Vera Plant into Casein Micelles

“…The anthraquinones extract from aloe vera (AQ) also showed strong -OH band-like standards suggesting the presence of anthraquinones in extracted powder. Conversely, in the case of FDP and SDP, the intensity of the -OH band was reduced considerably, probably due to the absence of anthraquinones [ 67 ] resulting from the deacetylation of bioactives [ 14 ]. Two bands at 2989 cm −1 and 2899 cm −1 are related to C-H symmetric stretching and asymmetric stretching of methylene (CH 2 ), respectively, indicating long aliphatic chains (-CH) of anthraquinones [ 68 ] in samples (aloin, aloe-emodin, rhein, AQ).…”

“…Aloe vera ( Aloe barbadensis ) leaves were collected from Aloe vera Australia (Goodman International, Brisbane, Australia). Whole leaf Aloe vera gel extracts and their spray-dried and freeze-dried powders were prepared by the method described previously [ 14 ]. Standards of Aloin (Mikromol, item code: MM1318.01, CAS# 1415-73-2), Aloe-emodin (TRC, item code: A575400-10MG, CAS #481-72-1), and Rhein CRS (EDQM, item code: EPY0002159, CAS# 478-43-3) were purchased from Novachem pty Ltd. (25 Carissane Road, Heidelberg West, Victoria, Australia).…”

“…The capability of casein micelles to encapsulate anthraquinones extracted from different Aloe vera samples which are sensitive to temperature, pH and oxidation [ 14 ] was investigated in the present study. Although casein micelles are cheap, sustainable and nutritious encapsulation vehicles for the protection of anthraquinones, it is necessary to understand the interactions and structural changes that occur during ultrasonication-assisted encapsulation.…”

“…Moreover, ultrasonication enhanced the binding of anthraquinones inside the casein micelles by hydrophobic interactions. Lower encapsulation efficiencies of FDP and SDP [ 14 ] were related to their accommodation on the hydrophilic surface of CM (superficial attachment) through hydrogen bonding during encapsulation.…”

“…In our previous study, it was reported that the degradation of these anthraquinones starts right after harvesting the Aloe vera leaves and continues to decompose during processing and storage [ 14 ]. So, encapsulating these anthraquinones seems to be an efficient method for food formulators while developing traditional medicines, functional foods, and nutraceuticals.…”