Identification and functional characterization of a novel aldo-keto reductase from Aloe vera.

MAIN CONCLUSION: The present investigation profoundly asserted the catalytic potential of plant-based aldo-ketoreductase, postulating its role in polyketide biosynthesis and providing new insights for tailored biosynthesis of vital plant polyketides for therapeutics. Plants hold great potential as a future source of innovative biocatalysts, expanding the possibilities within chemical reactions and generating a variety of benefits. The aldo-keto reductase (AKR) superfamily includes a huge collection of NAD(P)H-dependent oxidoreductases that carry out a variety of redox reactions essential for biosynthesis, detoxification, and intermediary metabolism. The present study involved the isolation, cloning, and purification of a novel aldo-ketoreductase (AvAKR) from the leaves of Aloe vera (Aloe barbadensis Miller) by heterologous gene expression in Escherichia coli based on the unigene sequences of putative ketoreductase and cDNA library screening by oligonucleotide hybridization. The in-silico structural analysis, phylogenetic relationship, and molecular modeling were outranged to approach the novelty of the sequence. Additionally, agroinfiltration of the candidate gene tagged with a green fluorescent protein (GFP) was employed for transient expression in the Nicotiana benthamiana to evaluate the sub-cellular localization of the candidate gene. The AvAKR preferred cytoplasmic localization and shared similarities with the known plant AKRs, keeping the majority of the conserved active-site residues in the AKR superfamily enzymes. The enzyme facilitated the NADPH-dependent reduction of various carbonyl substrates, including benzaldehyde and sugars, proclaiming a broad spectrum range. Our study successfully isolated and characterized a novel aldo-ketoreductase (AvAKR) from Aloe vera, highlighting its versatile NADPH-dependent carbonyl reduction proficiency therewith showcasing its potential as a versatile biocatalyst in diverse redox reactions.

The dark side of miracle plant-Aloe vera: a review.

BACKGROUND: Aloe vera (Aloe barbadensis Miller), commonly known as Ghritkumari/Gwarpatha, is a member of the Liliaceae family, used in the traditional medicine system for ages. Aloe vera has made its importance as a therapeutic agent, acting as a cure for various diseases such as skin problems, lungs, and heart disorders, diabetes, ulcers, various microbial infections, and asthma. Despite its tremendous health benefits, the dark side of the plant is a reason of concern as there are several active compounds present in the plant, raising questions on its safe oral consumption and application. METHODS AND RESULTS: The literature review was compiled from information resourced from various national and international journals available at Google Scholar and curated with Mendeley. The data mining was carried out during the period of January to May 2021. This study explored and summarized the dark side of Aloe vera, subjected to various secondary metabolites present in it. Aloin, the most active compound of Aloe vera, is a type of anthraquinone metabolized by human gut microflora, resulting in the formation of aloe-emodin anthraquinone, later being associated with several harmful effects such as carcinogenicity, genotoxicity, nephrotoxicity, and purgative. Besides this, several alkaloids and polysaccharides present in the plant are reported to cause hepatotoxicity and male infertility, respectively. CONCLUSIONS: The harmful effects of the plants are not adequately discovered yet; hence there is a need to come up with some mechanism to understand and suppress the formation of such toxic compounds completely. This review examined the botany, active compounds, and adverse clinical effects in the range of metabolites associated with this herb - "Aloe vera".