Kokum: A potential source of hydroxycitric acid, anthocyanin, and phenolic compounds

Image Source: University of Queensland https://www.uq.edu.au/

Kokum (Garcinia indica), is a medicinally important, underexploited tree species that is native to the Western Ghats of India. The fruits of Garcinia indica are globose or spherical in shape, dark purple in color in ripened stage with myriad health-promoting properties. Ayurveda, it has antidiabetic, anthelmintic, cardiotonic, and antiobesity properties. They are also useful in piles, dysentery, tumor, pain, and heart ailments. The dried rind of Garcinia indica is traditionally used as a culinary spice to provide a sour taste to food and is also widely used for the preparation of welcome drinks. The savory taste of the fruit is imparted by a major organic acid component called hydroxycitric acid (HCA), which is a potential anti-obesity agent and widely used in anti-obesity medicines.

 The purple color of the Garcinia indica fruit rind is mainly due to anthocyanin. Anthocyanin pigments are responsible for the red, blue, and purple colors of many fruits, vegetables, flowers, and cereal grains. Anthocyanin is considered a potential replacement for synthetic colors because of their brightness and water solubility, which allows their easy incorporation into aqueous food systems. There is a huge demand for natural food colorants and anthocyanin can be a potent alternative to synthetic dyes which takes care of consumer concerns over the use of synthetic additives. With the increasing interest in natural and biologically active compounds as a substitute for synthetic chemicals in the food industry, anthocyanin offers a particularly attractive option.

Apart from anthocyanin, Garcinia indica also contains other phenolic compounds like phenolic acid and flavonoids and could serve as natural sources for these compounds. These bioactive phenolic compounds have a wide range of biological activities: antioxidant, anti-microbial, antityrosinase,  anticholinesterase, anti-inflammatory, anti-cancerous, antihyperglycemic/antidiabetic, and antinociceptive activities which ensure enormous role as a natural food preservative, cosmetics and curing and preventing many diseases.

Indigenous fruits and vegetables are a major source of nutrition and exploration of them as natural plant-based raw materials for use in the food and pharmaceutical industry has received the attention of researchers. In the present study, principal bioactive compounds present in the 6 accessions of G. indica, an edible fruit of medicinal value, were investigated using liquid chromatography-mass spectrometry (LC-MS). This information about the bioactive compounds would help in the effective utilization of Garcinia indica fruit as nutraceuticals in the food and pharmaceutical industries.

The fruits were particularly rich in hydroxycitric acid (15.60%–22.92%), which makes them a suitable candidate for weight-loss supplements. The fruit rinds of G. cambogia is a prime natural source of HCA (10-30%) for commercial extraction. The extent of HCA  in G. indica “Vengrula”  was found to be comparable to G. cambogia, thus it could also be used as a source of HCA for commercial extraction.

Anthocyanin yield is a very important quality parameter as well as a key attribute from the industrial point of view. As pigments, they are almost exclusively responsible for the red color in fruits. In the present study, all the accessions showed very high anthocyanin content (4.47–7.08 mg g−1), a value much higher than that recorded for the majority of fruits and vegetables, which makes the fruit a good source of natural colour. Thirty phenolic compounds were successfully separated, identified, and quantified; these included para and ortho coumaric acid, naringenin, and apigenin. These compounds are known to be natural preservatives and anti-browning and therapeutic agents. Two-way hierarchal cluster analysis was performed and six accessions fell into two clusters: one comprised G. indica “Red” and “IIHR-2”, both rich in total phenols and with high antioxidant potential, whereas the other comprised accessions were low in total phenols and with poor antioxidant potential, namely G. indica “Local”, “Amruth Kokum”, “Vengurla”, and “IIHR-1”, although G. indica “Local” and “Vengurla” were rich in HCA. Heat map enabled easy depiction of the variability of analyzing parameters among the accessions. For example, G. indica “IIHR-2” found to be the richest source of anthocyanin, coumaric acid, naringenin, and apigenin which was clearly visible in the heat map. Two-way hierarchal clustering and a heat map helped in choosing the best accessions with optimal quality parameters. Overall, the present study highlights G. indica as a rich, new, and sustainable source of bioactive substances with food, pharmaceutical, and other industrial applications.

Further Reading: https://doi.org/10.1016/j.lwt.2021.112999

Authors: Pritee Singh and C. Kanupriya, ICAR-IIHR, Bengaluru

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