Biosynthesis of polyprenylated xanthones in Hypericum perforatum roots involves 4-prenyltransferase.

Polyprenylated xanthones are natural products with a multitude of biological and pharmacological activities. However, their biosynthetic pathway is not completely understood. In this study, metabolic profiling revealed the presence of 4-prenylated 1,3,5,6-tetrahydroxyxanthone derivatives in St. John's wort (Hypericum perforatum) root extracts. Transcriptomic data mining led to the detection of 5 variants of xanthone 4-prenyltransferase (HpPT4px) comprising 4 long variants (HpPT4px-v1 to HpPT4px-v4) and 1 short variant (HpPT4px-sh). The full-length sequences of all 5 variants were cloned and heterologously expressed in yeast (Saccharomyces cerevisiae). Microsomes containing HpPT4px-v2, HpPT4px-v4, and HpPT4px-sh catalyzed the addition of a prenyl group at the C-4 position of 1,3,5,6-tetrahydroxyxanthone; 1,3,5-trihydroxyxanthone; and 1,3,7-trihydroxyxanthone, whereas microsomes harboring HpPT4px-v1 and HpPT4px-v3 additionally accepted 1,3,6,7-tetrahydroxyxanthone. HpPT4px-v1 produced in Nicotiana benthamiana displayed the same activity as in yeast, while HpPT4px-sh was inactive. The kinetic parameters of HpPT4px-v1 and HpPT4px-sh chosen as representative variants indicated 1,3,5,6-tetrahydroxyxanthone as the preferred acceptor substrate, rationalizing that HpPT4px catalyzes the first prenylation step in the biosynthesis of polyprenylated xanthones in H. perforatum. Dimethylallyl pyrophosphate was the exclusive prenyl donor. Expression of the HpPT4px transcripts was highest in roots and leaves, raising the question of product translocation. C-terminal yellow fluorescent protein fusion of HpPT4px-v1 localized to the envelope of chloroplasts in N. benthamiana leaves, whereas short, truncated, and masked signal peptides led to the disruption of plastidial localization. These findings pave the way for a better understanding of the prenylation of xanthones in plants and the identification of additional xanthone-specific prenyltransferases.

The 'emodin family' of fungal natural products-amalgamating a century of research with recent genomics-based advances.

Covering: up to 2022A very large group of biosynthetically linked fungal secondary metabolites are formed via the key intermediate emodin and its corresponding anthrone. The group includes anthraquinones such as chrysophanol and cladofulvin, the grisandienes geodin and trypacidin, the diphenyl ether pestheic acid, benzophenones such as monodictyphenone and various xanthones including the prenylated shamixanthones, the agnestins and dimeric xanthones such as the ergochromes, cryptosporioptides and neosartorin. Such compounds exhibit a wide range of bioactivities and as such have been utilised in traditional medicine for centuries, as well as garnering more recent interest from the pharmaceutical sector. Additional interest comes from industries such as textiles and cosmetics due to their use as natural colourants. A variety of biosynthetic routes and mechanisms have been proposed for this family of compounds, being altered and updated as new biosynthetic methods develop and new results emerge. After nearly 100 years of such research, this review aims to provide a comprehensive overview of what is currently known about the biosynthesis of this important family, amalgamating the early chemical and biosynthetic studies with the more recent genetics-based advances and comparative bioinformatics.

Identification and characterization of glycosyltransferases catalyzing direct xanthone 4-C-glycosylation in Hypericum perforatum.

Xanthones are compounds with a diphenyl ether skeleton mainly found in plants and often glycosylated at carbon atoms. Although many C-glycosyltransferases (CGTs) participating in flavone C-glycosylation have been identified, MiCGT from Mangifera indica, adding sugar to an open-chain benzophenone skeleton, is the only identified xanthone biosynthesis-related CGT. Here, we identified two CGTs from Hypericum perforatum that add sugar to the closed-ring xanthone, but not benzophenone. These CGTs catalyze sugar transfer to the C-4 position of norathyriol (1,3,6,7-tetrahydroxyxanthone) to form isomangiferin (1,3,6,7-tetrahydroxyxanthone 4-C-glucoside), a major xanthone C-glucoside. This is the first study to report CGTs that mediate the direct C-glycosylation of xanthone.

Cytosolic aromatic aldehyde dehydrogenase provides benzoic acid for xanthone biosynthesis in Hypericum.

Benzoic acid is a building block of a multitude of well-known plant natural products, such as paclitaxel and cocaine. Its simple chemical structure contrasts with its complex biosynthesis. Hypericum species are rich in polyprenylated benzoic acid-derived xanthones, which have received attention due to their biological impact on human health. The upstream biosynthetic sequence leading to xanthones is still incomplete. To supply benzoic acid for xanthone biosynthesis, Hypericum calycinum cell cultures use the CoA-dependent non-ß-oxidative pathway, which starts with peroxisomal cinnamate CoA-ligase (HcCNL). Here, we use the xanthone-producing cell cultures to identify the transcript for benzaldehyde dehydrogenase (HcBD), a pivotal player in the non-ß-oxidative pathways. In addition to benzaldehyde, the enzyme efficiently catalyzes the oxidation of trans-cinnamaldehyde in vitro. The enzymatic activity is strictly dependent on the presence of NAD+ as co-factor. HcBD is localized to the cytosol upon ectopic expression of reporter fusion constructs. HcBD oxidizes benzaldehyde, which moves across the peroxisome membrane, to form benzoic acid. Increases in the HcCNL and HcBD transcript levels precede the elicitor-induced xanthone accumulation. The current work addresses a crucial step in the yet incompletely understood CoA-dependent non-ß-oxidative route of benzoic acid biosynthesis. Addressing this step may offer a new biotechnological tool to enhance product formation in biofactories.

A promiscuous coenzyme A ligase provides benzoyl-coenzyme A for xanthone biosynthesis in Hypericum.

Benzoic acid-derived compounds, such as polyprenylated benzophenones and xanthones, attract the interest of scientists due to challenging chemical structures and diverse biological activities. The genus Hypericum is of high medicinal value, as exemplified by H. perforatum. It is rich in benzophenone and xanthone derivatives, the biosynthesis of which requires the catalytic activity of benzoate-coenzyme A (benzoate-CoA) ligase (BZL), which activates benzoic acid to benzoyl-CoA. Despite remarkable research so far done on benzoic acid biosynthesis in planta, all previous structural studies of BZL genes and proteins are exclusively related to benzoate-degrading microorganisms. Here, a transcript for a plant acyl-activating enzyme (AAE) was cloned from xanthone-producing Hypericum calycinum cell cultures using transcriptomic resources. An increase in the HcAAE1 transcript level preceded xanthone accumulation after elicitor treatment, as previously observed with other pathway-related genes. Subcellular localization of reporter fusions revealed the dual localization of HcAAE1 to cytosol and peroxisomes owing to a type 2 peroxisomal targeting signal. This result suggests the generation of benzoyl-CoA in Hypericum by the CoA-dependent non-ß-oxidative route. A luciferase-based substrate specificity assay and the kinetic characterization indicated that HcAAE1 exhibits promiscuous substrate preference, with benzoic acid being the sole aromatic substrate accepted. Unlike 4-coumarate-CoA ligase and cinnamate-CoA ligase enzymes, HcAAE1 did not accept 4-coumaric and cinnamic acids, respectively. The substrate preference was corroborated by in silico modeling, which indicated valid docking of both benzoic acid and its adenosine monophosphate intermediate in the HcAAE1/BZL active site cavity.

Cytotoxic xanthones isolated from Calophyllum depressinervosum and Calophyllum buxifolium with antioxidant and cytotoxic activities.

The stem bark of Calophyllum depressinervosum and Calophyllum buxifolium were extracted and examined for their antioxidant activities, together with cytotoxicity towards human cancer cells. The methanol extract of C. depressinervosum exhibited good DPPH and NO scavenging effects. The strongest BCB inhibition and FIC effects were shown by dichloromethane and ethyl acetate extracts of both species. Overall, DPPH, FRAP and FIC assays showed strong correlation with TPC. For cytotoxicity, hexane extract of C. depressinervosum possessed the strongest anti-proliferative activities towards SNU-1 cells while the hexane extract of C. buxifolium showed the strongest activity towards LS-174T and K562 cells with the IC50 values ranging from 7 to 17 µg/mL. The purification of plant extracts afforded eight xanthones, ananixanthone (1), caloxanthone B (2), caloxanthone I (3), caloxanthone J (4) xanthochymone B (5), thwaitesixanthone (6), 1,3,5,6-tetrahydroxyxanthone (7) and dombakinaxanthone (8). All the xanthones, except 1 were reported for the first time from both Calophyllum species. The xanthones were examined for their cytotoxic effect against K562 leukemic cells. Compounds 1 and 2 showed strong cytotoxicity with the IC50 values of 2.96 and 1.23 µg/mL, respectively. The molecular binding interaction of 2 was further investigated by performing molecular docking study with promising protein receptor Src kinase.

Chemical fingerprint analysis and metabolic profiling of 50% ethanol fraction of Lomatogonium rotatum by ultra-performance liquid chromatography/quadrupole-time of flight mass spectrometry.

Lomatogonium rotatum (L.) Fries ex Nym (L. rotatum), a member of Gentianaceae, is an important mongolian medicine in China used to treat febrile diseases in liver and gallbladder. The aim of present study was to investigate the chemical constituents and metabolites of the 50% ethanol fraction of L. rotatum (50EtLR). Firstly, the extract of L. rotatum was partitioned by macroporous resin to obtain the target fraction (50EtLR), then several compounds were isolated from 50EtLR to obtained the standards for further analysis of chemical constituents of 50EtLR. Secondly, the chemical constituents of 50EtLR were characterized using the ultra-high performance liquid chromatography coupled with quadrupole-time-of-flight mass spectrometry (UHPLC-Q-TOF-MS/MS). Finally, prototype constituents and related metabolites were analyzed after orally administerng 50EtLR to rats. As a result, a new compound, 6-O-[ß-d-xylopyranosyl-(1 → 6)-O-ß-d-glucopyranosyl]-1,4,8-trimethoxyxanthone (6) along with seven known compounds (1-5, 7 and 8) were isolated from the 50EtLR, 92 components were either unambiguously or tentatively identified. Additionally, 34 prototype constituents and 112 metabolites in rat plasma along with 32 prototype constituents and 53 metabolites in rat liver were tentatively identified. Therefore, xanthones and flavonoids were the main chemical constituents of 50EtLR and sulfation and glucuronidation are the main enzyme-induced metabolic pathways involved post-administration.

Effects of Benzophenones from Mango Leaves on Lipid Metabolism.

The mango tree (Mangifera indica L.) is a tropical, perennial, woody evergreen plant belonging to the Anacardiaceae. In traditional medicine, dried mango tree leaves were considered useful in treating diabetes and respiratory infections. In this paper, we review the phytochemical research on mango leaves and the mechanisms of benzophenones in lipid metabolism regulation. Thirty-six benzophenones have been isolated from mango leaves; among them, mangiferin is the major compound. Structure-activity relationships of benzophenones in lipid accumulation and the mechanisms of action of mangiferin in lipid metabolism are summarized. After oral administration, mangiferin is partly converted to its active metabolite, northyariol, which contributes to the activation of sirtuin-1 and liver kinase B1 and increases the intracellular AMP level and AMP/adenosine triphosphate ratio, followed by AMP-activated protein kinase phosphorylation, leading to increased phosphorylation of sterol regulatory element-binding protein-1c. Current evidence supports ethnopharmacological uses of mango leaves in diabetes and points toward potential future applications.

Cellular antioxidant activity and in vitro intestinal permeability of phenolic compounds from four varieties of mango bark (Mangifera indica L.).

BACKGROUND: Mango bark is an important agro-industrial residue from mango pruning. In traditional medicine, the aqueous extract from mango bark (MBE) has been used in ethnomedicine for the treatment of many diseases. However, there is scarce information using cellular models to evaluate the potential use of this plant material for human consumption. In this study, the phenolic content from the MBE from four varieties (Kent, Keitt, Ataulfo and Tommy Atkins) was analyzed by high-performance liquid chromatography coupled to photodiode array detector (HPLC-DAD) and liquid chromatography coupled with time-of-flight mass spectrometry (LC/MS-TOF). Additionally, the cellular antioxidant activity of the MBE from the four mango varieties were compared. Finally, the intestinal permeability of the main polyphenols found in the MBE (mangiferin and gallic acid) was evaluated. RESULTS: Mangiferin and gallic acid were the main constituents in the MBE from the four mango varieties. Furthermore, the Ataulfo variety showed the highest cellular antioxidant activity (67%) at the concentration of 100 µg mL−1 . The intestinal permeability of mangiferin present in the bark extracts was 3- to 4.8-fold higher than those of mangiferin as standard, whereas the intestinal permeability of gallic acid varied among the tested extracts. CONCLUSION: MBE has the potential to exert antioxidant activity at the cellular level and can have an impact on human health. It may also be a good source for the extraction of polyphenols mainly mangiferin.

Penicillixanthone A, a marine-derived dual-coreceptor antagonist as anti-HIV-1 agent.

Marine micro-organisms have been proven to be excellent sources of bioactive compounds against HIV-1. Several natural products obtained from marine-derived Aspergillus fungi were screened for their activities to inhibit HIV-1 infection. Penicillixanthone A (PXA), a natural xanthone dimer from jellyfish-derived fungus Aspergillus fumigates, displayed potent anti-HIV-1 activity by inhibiting infection against CCR5-tropic HIV-1 SF162 and CXCR4-tropic HIV-1 NL4-3, with IC50 of 0.36 and 0.26 µM, respectively. Molecular docking study was conducted to understand the possible binding mode of PXA with the CCR5/CXCR4. The results revealed that, the marine-derived PXA, as a CCR5/CXCR4 dual-coreceptor antagonist, presents a new type of potential lead product for the development of anti-HIV therapeutics.

Sequential regiospecific gem-diprenylation of tetrahydroxyxanthone by prenyltransferases from Hypericum sp.

Polyprenylated acylphloroglucinol derivatives, such as xanthones, are natural plant products with interesting pharmacological properties. They are difficult to synthesize chemically. Biotechnological production is desirable but it requires an understanding of the biosynthetic pathways. cDNAs encoding membrane-bound aromatic prenyltransferase (aPT) enzymes from Hypericum sampsonii seedlings (HsPT8px and HsPTpat) and Hypericum calycinum cell cultures (HcPT8px and HcPTpat) were cloned and expressed in Saccharomyces cerevisiae and Nicotiana benthamiana, respectively. Microsomes and chloroplasts were used for functional analysis. The enzymes catalyzed the prenylation of 1,3,6,7-tetrahydroxyxanthone (1367THX) and/or 1,3,6,7-tetrahydroxy-8-prenylxanthone (8PX) and discriminated nine additionally tested acylphloroglucinol derivatives. The transient expression of the two aPT genes preceded the accumulation of the products in elicitor-treated H. calycinum cell cultures. C-terminal yellow fluorescent protein fusions of the two enzymes were localized to the envelope of chloroplasts in N. benthamiana leaves. Based on the kinetic properties of HsPT8px and HsPTpat, the enzymes catalyze sequential rather than parallel addition of two prenyl groups to the carbon atom 8 of 1367THX, yielding gem-diprenylated patulone under loss of aromaticity of the gem-dialkylated ring. Coexpression in yeast significantly increased product formation. The patulone biosynthetic pathway involves multiple subcellular compartments. The aPTs studied here and related enzymes may be promising tools for plant/microbe metabolic pathway engineering.

Aspergixanthones I⁻K, New Anti-Vibrio Prenylxanthones from the Marine-Derived Fungus Aspergillus sp. ZA-01.

Marine-derived fungi are a rich source of structurally diverse metabolites. Fungi produce an array of compounds when grown under different cultivation conditions. In the present work, different media were used to cultivate the fungus Aspergillus sp. ZA-01, which was previously studied for the production of bioactive compounds, and three new prenylxanthone derivatives, aspergixanthones I⁻K (1⁻3), and four known analogues (4⁻7) were obtained. The absolute configuration of 1 was assigned by ECD experiment and the Mo2(AcO)4 ICD spectrum of its methanolysis derivative (1a). All the compounds (1⁻7) were evaluated for their anti-Vibrio activities. Aspergixanthone I (1) showed the strongest anti-Vibrio activity against Vibrio parahemolyticus (MIC = 1.56 µM), Vibrio anguillarum (MIC = 1.56 µM), and Vibrio alginolyticus (MIC = 3.12 µM).

Chitosan oligosaccharides affect xanthone and VOC biosynthesis in Hypericum perforatum root cultures and enhance the antifungal activity of root extracts.

KEY MESSAGE: Water-soluble chitosan oligosaccharides (COS) affect xanthone and volatile organic compound content, as well as antifungal activity against human pathogenic fungi of extracts obtained from Hypericum perforatum root cultures. Several studies have demonstrated the elicitor power of chitosan on xanthone biosynthesis in root cultures of H. perforatum. One of the major limitations to the use of chitosan, both for basic and applied research, is the need to use acidified water for solubilization. To overcome this problem, the elicitor effect of water-soluble COS on the biosynthesis of both xanthones and volatile organic compounds (VOCs) was evaluated in the present study. The analysis of xanthones and VOCs was performed by HPLC and GC-MS headspace analysis. The obtained results showed that COS are very effective in enhancing xanthone biosynthesis. With 400 mg L-1 COS, a xanthone content of about 30 mg g-1 DW was obtained. The antifungal activity of extracts obtained with 400 mg L-1 COS was the highest, with MIC50 of 32 µg mL-1 against Candida albicans and 32-64 µg mL-1 against dermatophytes, depending on the microorganism. Histochemical investigations suggested the accumulation of isoprenoids in the secretory ducts of H. perforatum roots. The presence of monoterpenes and sesquiterpenes was confirmed by the headspace analysis. Other volatile hydrocarbons have been identified. The biosynthesis of most VOCs showed significant changes in response to COS, suggesting their involvement in plant-fungus interactions.

Metabolism, pharmacokinetics, and hepatic disposition of xanthones and saponins on Zhimu treatments for exploratively interpreting the discrepancy between the herbal safety and timosaponin A3-induced hepatotoxicity.

Timosaponin A3, a saponin in Zhimu, elicited hepatotoxicity via oxidative stress. However, the clinical medication of Zhimu has been historically regarded as safe, probably associated with the antioxidants it contains. However, the related information on the in vivo levels of timosaponin A3 and antioxidants remained unclear on Zhimu treatments. Therefore, a combination of the in vitro metabolism, including microbiota-mediated and liver-mediated metabolism, and in vivo pharmacokinetics and hepatic disposition, was conducted for three xanthones (neomangiferin, mangiferin, and norathyriol) and three saponins (timosaponin B2, timosaponin B3, and timosaponin A3) on Zhimu treatments. Consequently, following oral administration of Zhimu decoction to rats, those saponins and xanthones were all observed in the plasma with severe liver first-pass effect, where mangiferin was of the maximum exposure. Despite the ignorable content in the herb, timosaponin A3 elicited sizable hepatic exposure as the microbiota-mediated metabolite of saponins in Zhimu. The similar phenomenon also occurred to norathyriol, the microbiota-mediated metabolite of xanthones. However, the major prototypes in Zhimu were of limited hepatic exposure. We deduced the hepatic collection of norathyriol, maximum circulating levels of mangiferin, and timosaponin B2 and mangiferin interaction may directly or indirectly contribute to the whole anti-oxidation of Zhimu, and then resisted the timosaponin A3-induced hepatotoxicity. Thus, our study exploratively interpreted the discrepancy between herbal safety and timosaponin A3-induced hepatotoxicity. However, given the considerable levels and slow eliminated rate of timosaponin A3 in the liver, more attention should be paid to the safety on the continuous clinical medication of Zhimu in the future.

Virtual screening, Docking, ADMET and System Pharmacology studies on Garcinia caged Xanthone derivatives for Anticancer activity.

Caged xanthones are bioactive compounds mainly derived from the Garcinia genus. In this study, a structure-activity relationship (SAR) of caged xanthones and their derivatives for anticancer activity against different cancer cell lines such as A549, HepG2 and U251 were developed through quantitative (Q)-SAR modeling approach. The regression coefficient (r2), internal cross-validation regression coefficient (q2) and external cross-validation regression coefficient (pred_r2) of derived QSAR models were 0.87, 0.81 and 0.82, for A549, whereas, 0.87, 0.84 and 0.90, for HepG2, and 0.86, 0.83 and 0.83, for U251 respectively. These models were used to design and screened the potential caged xanthone derivatives. Further, the compounds were filtered through the rule of five, ADMET-risk and synthetic accessibility. Filtered compounds were then docked to identify the possible target binding pocket, to obtain a set of aligned ligand poses and to prioritize the predicted active compounds. The scrutinized compounds, as well as their metabolites, were evaluated for different pharmacokinetics parameters such as absorption, distribution, metabolism, excretion, and toxicity. Finally, the top hit compound 1G was analyzed by system pharmacology approaches such as gene ontology, metabolic networks, process networks, drug target network, signaling pathway maps as well as identification of off-target proteins that may cause adverse reactions.

Antioxidant xanthones and anthraquinones isolated from a marine-derived fungus Aspergillus versicolor.

Chemical examination of an EtOAc extract of cultured Aspergillus versicolor fungus from deep-sea sediments resulted in the isolation of four xanthones, eight anthraquinones and five alkaloids, including a new xanthone, oxisterigmatocystin D (1) and a new alkaloid, aspergillusine A (13). High resolution electron impact mass spectrometry (HR-EI-MS), FT-IR spectroscopy, and NMR techniques were used to elucidate the structures of these compounds, and the absolute configuration of compound 1 was established by its NMR features and coupling constant. Furthermore, the biosynthesis pathway of these xanthones and anthraquinones were deduced, and their antioxidant activity and cytotoxicity in human cancer cell lines (HTC-8, Bel-7420, BGC-823, A549, and A2780) were evaluated. The trolox equivalent antioxidant capacity (TEAC) assay indicated most of the xanthones and anthraquinones possessing moderate antioxidant activities. The Nrf2-dependent luciferase reporter gene assay revealed that compounds 6, 7, 9, and 12 potentially activated the expression of Nrf2-regulated gene. In addition, compounds 5 and 11 showed weak cytotoxicity on A549 with the IC50 values of 25.97 and 25.60 µmol·L-1, respectively.

Exodermis and endodermis are the sites of xanthone biosynthesis in Hypericum perforatum roots.

Xanthones are specialized metabolites with antimicrobial properties, which accumulate in roots of Hypericum perforatum. This medicinal plant provides widely taken remedies for depressive episodes and skin disorders. Owing to the array of pharmacological activities, xanthone derivatives attract attention for drug design. Little is known about the sites of biosynthesis and accumulation of xanthones in roots. Xanthone biosynthesis is localized at the transcript, protein, and product levels using in situ mRNA hybridization, indirect immunofluorescence detection, and high lateral and mass resolution mass spectrometry imaging (AP-SMALDI-FT-Orbitrap MSI), respectively. The carbon skeleton of xanthones is formed by benzophenone synthase (BPS), for which a cDNA was cloned from root cultures of H. perforatum var. angustifolium. Both the BPS protein and the BPS transcripts are localized to the exodermis and the endodermis of roots. The xanthone compounds as the BPS products are detected in the same tissues. The exodermis and the endodermis, which are the outermost and innermost cell layers of the root cortex, respectively, are not only highly specialized barriers for controlling the passage of water and solutes but also preformed lines of defence against soilborne pathogens and predators.

Production of an emericellin and its analogues as fungal biological responses for Shimbu-to extract.

This research examined the production of fungal metabolites as a biological response to Kampo medicines. Shimbu-to (SMB) is a Kampo medicine composed of five herbal components: peony root (Shakuyaku), ginger (Shokyo), processed aconite root (Bushi), Poria sclerotium (Bukuryo), and Atractylodes lancea rhizomes (Sojutsu). High-performance liquid chromatography (HPLC) analysis of the fungus Aspergillus nidulans CBS 112.46 incubated in potato dextrose broth supplemented with SMB extract revealed emericellin (2) as the major peak and new xanthone analogues 24-hydroxyshamixanthone (1), shamixanthone (3), epishamixanthone (4), pre-shamixanthone (5), and variecoxanthone A (6) as minor peaks. The structure of 1 was determined by detailed analysis of 1D-NMR, 2D-NMR, and MS data. The results suggest that SMB extract regulates the biosynthesis of emericellin and its analogues in A. nidulans. Further investigations revealed that glucose induces the biosynthesis of emericellin and its analogues in A. nidulans in a concentration-dependent manner.

Dynamics in the concentrations of health-promoting compounds: lupeol, mangiferin and different phenolic acids during postharvest ripening of mango fruit.

BACKGROUND: Mango fruit (Mangifera indica L.) is renowned for its pleasant taste and as a rich source of health beneficial compounds. The aim of this study was to investigate the changes in concentrations of health-promoting compounds, namely ascorbic acid, carotenoids, antioxidants, lupeol, mangiferin, total phenols and individual phenolic acids, as well as ethylene production and respiration rates during climacteric ripening in 'Kensington Pride' and 'R2E2' mango fruit. RESULTS: The climacteric ethylene and respiration peaks were noted on the third day of the fruit ripening period. The concentrations of total carotenoids in the pulp, total antioxidants in both pulp and peel, and total phenols of the peel, lupeol and mangiferin were significantly elevated, whereas the concentration of ascorbic acid declined during post-climacteric ripening. Gallic, chlorogenic and vanillic acids were identified as the major phenolic acids in both pulp and peel of 'Kensington Pride' and 'R2E2' mangoes. The concentrations of phenolic acids (gallic, chlorogenic, vanillic, ferulic and caffeic acids) also increased during the post-climacteric phase. The concentrations of all phenolic compounds were several-fold higher in the peel than pulp. CONCLUSION: Mangoes at post-climacteric ripening phase offer the highest concentrations of health-promoting compounds. Peel, at this stage of fruit ripening, could be exploited as a good source for extraction of these compounds. © 2017 Society of Chemical Industry.

Large-Scale Preparation of a Specific Xanthone from Swertia mussotii and Evaluation of Its α-Glucosidase Inhibitory Activity.

Large-scale preparation and α-glucosidase inhibitory activity of a specific xanthone swertioside from Swertia mussotii were investigated in this study. Firstly, an efficient method was successfully established by liquid-liquid extraction, preparative high-performance liquid chromatography and sephadex LH-20 for large-scale preparation of swertioside. The recovery of swertioside reached 92.0%. Secondly, in vitro α-glucosidase inhibition experiment showed that swertioside had good inhibition close to acarbose. The study showed that swertioside had potential use as an anti-diabetic agent.