Phytotoxic Constituents of the Fruits of Averrhoa carambola

Cytotoxic/antiproliferative and nutraceutical activity of aqueous and ethanolic extracts of green and mature Averrhoa carambola

Averrhoa carambola L. presents in its composition diversity of nutrients and vitamins. The present study aimed to extract water and fat-soluble compounds from this fruit at different stages of maturation (green and mature), perform the physical-chemical characterization as well as evaluate its cytotoxicity against hepatoma cells of Rattus norvegicus (HTC). The physicochemical results showed that the pH and molar acidity is influenced by the fruit maturation state. The fruit presented high percentage of moisture, while the percentage of total minerals (ash) increased according to its maturation stage. The results of the phytochemical screening showed that star fruits present phenolic compounds. The antioxidant activity showed greater potential for the ethanolic extracts of the green and mature star fruit. For HTC cells treated with ethanolic extract of green and mature star fruit the data show absence of cytotoxic effect. The tests with the aqueous extract showed cytotoxic/antiproliferative effect of green and mature star fruit extract, in 24, 48 and 72 hours. The presence of nutraceutical compounds and the cytotoxic/antiproliferative activity were more expressive in the aqueous extract, being an option of easily accessible solvent economic and not harmful to organisms.

Averrhoa carambola L. fruit and stem metabolites profiling and immunostimulatory action mechanisms against cyclosporine induced toxic effects in rat model as analyzed using UHPLC/MS-MS-based chemometrics and bioassays

The Averrhoa carambola L. tree encompasses a myriad of phytochemicals contributing to its nutritional and health benefits. The current study aims at investigating the A. carambola L. the metabolite profile grown in tropical and temperate regions represented by fruit and stem, for the first time using UPLC/MS-based molecular networking and chemometrics. Asides, assessment of the immunostimulatory effect of ripe fruit and stem, was compared in relation to metabolite fingerprints. Eighty metabolites were identified, 8 of which are first-time to be reported including 3 dihydrochalcone-C-glycosides, 4 flavonoids, and one phenolic. Multivariate data analysis revealed dihydrochalcones as origin-discriminating metabolites between temperate and tropical grown fruits. Further, an in vivo immunomodulatory assay in a cyclosporine A-induced rat model revealed a potential immune-enhancing effect as manifested by down-regulation of inflammatory markers (IL-6, INF-γ, IL-1, TLR4, and ESR) concurrent with the up-regulation of CD4 level and the CD4/CD8 ratio. Moreover, both extracts suppressed elevation of liver and kidney functions in serum as well as reduction in oxidative stress with concurrent increased levels of T-protein, albumin, globulin, and A/G ratio. This study pinpoints differences in secondary metabolite profiles amongst A. carambola L. accessions from different origins and organ type and its immunomodulatory action mechanisms.

Averrhoa carambola L., Cyphomandra betacea, Myrciaria dubia as a Source of Bioactive Compounds of Antioxidant Properties

Natural bioactive compounds play an important role in the prevention of various diseases. The exotic fruits Averrhoa carambola L. (star fruit), Cyphomandra betacea (tamarillo) and Myrciaria dubia (camu-camu) can be valuable sources of phytochemicals with antioxidant properties. The aim of this study has been to compare the antioxidant properties of these exotic fruits, the structure of polyphenolic compounds and the content of vitamin C and β-carotene. All the juices were analyzed for their antioxidant capacity (DPPH and ABTS assays) and the composition of phenolic compounds (TP and FBBB assays, total flavonoid content, total anthocyanins). In addition, HPLC assays were performed to analyse the content of phenolic acids, flavonoids, vitamin C and β-carotene. The results demonstrated that juice from the Myrciaria dubia fruit had the highest antioxidant capacity, which was 4.5-fold higher than that of juice from Averrhola carambola L., and nearly 7-fold higher than the antioxidant capacity of Cyphomandra betacea fruit juice. Additionally, juice from the camu-camu fruit had a 3- to 4-fold higher total polyphenol content (8290 ± 254 mg GAE L^-1) and a high level of vitamin C (8410.8 ± 16.9 mg AA kg^-1). In turn, tamarillo juice had a high content of total anthocyanins (5796 mg CGE L^-1) and phenolic acids (mostly chlorogenic acid and caffeic acid). Juice produced from carambola had a high content of total flavonoids (1345 mg CAE L^-1), and the composition of these compounds was dominated by flavanols (epicatechin). The research results justify the conclusion that fruits of Myrciaria dubia, Averrhoa carambola L., Cyphomandra betacea are rich sources of bioactive compounds with antioxidant properties, and in the near future may serve as healthful food ingredients.

Traditional Uses, Phytochemical Constituents and Pharmacological Properties of Averrhoa carambola L.: A Review

Averrhoa carambola L. (star fruit) is an edible fruit that is extensively cultivated in southern China, Southeast Asia, India, and northern South America. It has a sweet and juicy taste and is frequently used in fruit salads and fruit platters, as a garnish in cocktail drinks and beverages, or squeezed into juice and served as a beverage. Traditionally, it has been used for treating diabetes and diabetic nephropathy, arthralgia, vomiting, lithangiuria, coughing, hangovers, and chronic paroxysmal headache for thousands of years. Currently, approximately 132 compounds have been isolated from A. carambola. Among them, flavonoids, benzoquinone, and their glycosides have been considered as biologically active substances, which are responsible for various biological activities. Pharmacological studies have revealed that crude extracts or monomeric compounds from A. carambola exhibit multiple bioactivities, such as anti-oxidant, anti-hyperglycemic, anti-obesity, anti-hyperlipidemic, anti-tumor, anti-inflammatory, hepatoprotective, cardioprotective, anti-hypertensive, neuroprotective, and others. Thus, A. carambola is a valuable treatment in Chinese medicine with therapeutic potential for multiple diseases, especially diabetes and diabetes-related diseases. Even though it is a very promising candidate in the development of functional food and the pharmaceutical industry, reports on its bioactivities have only been conducted in vivo and in vitro and there is a gap in research regarding clinical settings and safety. This review therefore provides a comprehensive and systematic overview of current progress on botany, ethnopharmacology, phytochemistry, pharmacology, and toxicity of A. carambola, providing a valuable reference for further developments and applications of A. carambola in the pharmaceutical industry and functional food.

Two new glycosides from Panzerina lanata (L.) Soják

Two new glycosides, namely panalaside A (1) and panalaside B (2) were isolated from from Panzerina lanata (L.) Soják. The structures of 1 and 2 were elucidated by spectroscopic methods, including UV, IR, HR-ESI-MS and extensive 1 D and 2 D NMR techniques.

The genome sequence of star fruit (Averrhoa carambola)

Oxalidaceae is one of the most important plant families in horticulture, and its key commercially relevant genus, Averrhoa, has diverse growth habits and fruit types. Here, we describe the assembly of a high-quality chromosome-scale genome sequence for Averrhoa carambola (star fruit). Ks distribution analysis showed that A. carambola underwent a whole-genome triplication event, i.e., the gamma event shared by most eudicots. Comparisons between A. carambola and other angiosperms also permitted the generation of Oxalidaceae gene annotations. We identified unique gene families and analyzed gene family expansion and contraction. This analysis revealed significant changes in MADS-box gene family content, which might be related to the cauliflory of A. carambola. In addition, we identified and analyzed a total of 204 nucleotide-binding site, leucine-rich repeat receptor (NLR) genes and 58 WRKY genes in the genome, which may be related to the defense response. Our results provide insights into the origin, evolution and diversification of star fruit.

Isocoumarins and Dihydroisocoumarins From the Endophytic Fungus Biscogniauxia capnodes Isolated From the Fruits of Averrhoa carambola

An endophytic fungus Biscogniauxia capnodes was isolated from a popular edible fruit Averrhoa carambola. The fungus was fermented in potato dextrose broth for 3 weeks, and then the culture broth and mycelium were extracted with ethyl acetate. Chromatographic separation of this extract furnished 2 isocoumarins, reticulol (1) and 6- O-methyl-reticulol (2), and 2 dihydroisocoumarins, 5-methylmellein (3) and 7-hydroxy-5-methylmellein (4). Compound 1 showed moderate antioxidant activity against 2,2′-diphenyl-1-picrylhydrazyl radicals (IC50 value, 58 μg/mL). This is the first report of the isolation of B. capnodes as an endophyte, as well as the compounds 1 to 4 from B. capnodes.

Carotenoid-Derived Flavor Precursors from Averrhoa carambola Fresh Fruit

The fruit of Averrhoa carambola L. (Oxalidaceae), commonly known as star fruit or carambola, is popular in tropical and subtropical regions. Carotenoid-derived components, mainly C₁₃- and C₁₅-norisoprenoids, contribute greatly to the flavor of star fruit. Previously reported norisoprenoids were tentatively identified by GC-MS analysis after enzymatic hydrolysis. To gain accurate information about glycosidically bound flavor precursors in star fruit, a phytochemical study was conducted, which led to the isolation of 16 carotenoid derivatives—One new C₁₃-norisoprenoid glucoside, (5R,6S,7E,9R)-5,6,9-trihydroxy-7-megastigmene 9-O-β-d-glucoside (1); one new C₁₅-norisoprenoid, (6S,7E,10S)-Δ^9,15-10-hydroxyabscisic alcohol (11); and 14 known ones, of which 12 were in glucoside form. The structures of the two new compounds were elucidated on the basis of extensive spectroscopic data analysis and chemical reaction. Compound 11 was a rare C₁₅-norisoprenoid with a double bond between C-9 and C-15, and its possible biogenetic pathway was proposed. The known compounds were identified by comparison of their mass and nuclear magnetic resonance (NMR) data with those reported in the literature. The structure identification of one new (1) and seven known (3–7, 9, and 10) C₁₃-norisoprenoid glucosides from the genus Averrhoa for the first time enriches the knowledge of carotenoid-derived flavor precursors in star fruit.

Flavonoids isolated from the fresh sweet fruit of Averrhoa carambola, commonly known as star fruit

Thirteen flavonoids were isolated from the fresh sweet fruit of Averrhoa carambola L. (Oxalidaceae), commonly known as star fruit, and their structures were determined by spectroscopic and chemical methods. 8-Carboxymethyl-(+)-epicatechin methyl ester, pinobanksin 3-O-β-d-glucoside, and carambolasides M-Q were undescribed structures. (+)-Epicatechin, aromadendrin 3-O-β-d-glucoside, helicioside A, taxifolin 3'-O-β-d-glucoside, galangin 3-O-rutinoside, and isorhamnetin 3-O-rutinoside were reported from this species for the first time. Pinobanksin 3-O-β-d-glucoside and carambolasides M-Q showed more potent 2,2'-azinobis-(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical cation scavenging activity (IC₅₀ = 5.3-2.3 μM) than l-ascorbic acid (10.5 μM). Further, (+)-epicatechin, pinobanksin 3-O-β-d-glucoside, isorhamnetin 3-O-rutinoside, and carambolasides O-Q exhibited weak porcine pancreatic lipase inhibitory activity.

Heptyl vicianoside and methyl caramboside from sour star fruit

Two new alkyl glycosides, heptyl vicianoside (1) and methyl 2-O-β-d-fucopyranosyl-α-l-arabinofuranoside (methyl caramboside, 4), were isolated from the sour fruit of Averrhoa carambola L. (Oxalidaceae), along with octyl vicianoside (2), cis-3-hexenyl rutinoside (3), and methyl α-d-fructofuranoside (5). Their structures were determined by spectroscopic and chemical methods. Compounds 2, 3, and 5 were obtained from the genus Averrhoa for the first time. All the compounds were evaluated for in vitro α-glucosidase, pancreatic lipase, and acetylcholinesterase inhibitory activities, but none of them were potent.