Phenolic compounds from the flowers of Garcinia dulcis

A multiplex approach of MS, 1D-, and 2D-NMR metabolomics in plant ontogeny: A case study on Clusia minor L. organs (leaf, flower, fruit, and seed)

INTRODUCTION

The genus Clusia L. is mostly recognised for the production of prenylated benzophenones and tocotrienol derivatives.

OBJECTIVES

The objective of this study was to map metabolome variation within Clusia minor organs at different developmental stages.

MATERIAL AND METHODS

In total 15 organs/stages (leaf, flower, fruit, and seed) were analysed by UPLC-MS and 1H- and heteronuclear multiple-bond correlation (HMBC)-NMR-based metabolomics.

RESULTS

This work led to the assignment of 46 metabolites, belonging to organic acids(1), sugars(2) phenolic acids(1), flavonoids(3) prenylated xanthones(1) benzophenones(4) and tocotrienols(2). Multivariate data analyses explained the variability and classification of samples, highlighting chemical markers that discriminate each organ/stage. Leaves were found to be rich in 5-hydroxy-8-methyltocotrienol (8.5 μg/mg f.w.), while flowers were abundant in the polyprenylated benzophenone nemorosone with maximum level detected in the fully mature flower bud (43 μg/mg f.w.). Nemorosone and 5-hydroxy tocotrienoloic acid were isolated from FL6 for full structural characterisation. This is the first report of the NMR assignments of 5-hydroxy tocotrienoloic acid, and its maximum level was detected in the mature fruit at 50 μg/mg f.w. Seeds as typical storage organ were rich in sugars and omega-6 fatty acids.

CONCLUSION

To the best of our knowledge, this is the first report on a comparative 1D-/2D-NMR approach to assess compositional differences in ontogeny studies compared with LC-MS exemplified by Clusia organs. Results derived from this study provide better understanding of the stages at which maximal production of natural compounds occur and elucidate in which developmental stages the enzymes responsible for the production of such metabolites are preferentially expressed.

Cardiovascular Protective Effect of Garcinia dulcis Flower Acetone Extract in 2-Kidney-1-Clip Hypertensive Rats

Morelloflavone and camboginol are bioactive compounds purified from Garcinia dulcis (GD), which has anti-inflammatory and antihypertensive properties. The objective of this study was to examine the cardiovascular protective effect of GD flower acetone extract in 2-kidney-1-clip (2K1C) hypertensive rats. Male Wistar rats underwent 2K1C or sham operation (SO) and were housed for 4 weeks. Each group of rats, then, was further divided into 2 subgroups receiving oral administration of either 50 mg/kg BW GD extract or corn oil (vehicle) daily for 4 weeks. Noninvasive blood pressure (BP) and body weight were measured weekly throughout the study. Subsequently, the invasive measurement of arterial BP and the heart rate were determined in all anesthetized rats. The baroreceptor reflex sensitivity (BRS) was investigated by injection of either phenylephrine or sodium nitroprusside for bradycardia or tachycardia response, respectively. Histological examination of the heart and thoracic aorta was also performed in order to investigate the general morphology and the tumor necrosis factor alpha (TNF-α) expression. We found that the GD flower extract significantly diminished the BP and restored the impaired BRS. Moreover, it also decreased the TNF-α expression in the cardiac muscle and thoracic aorta of 2K1C when compared to the SO group. Taken together, our data showed that GD flower extract exhibits the cardiovascular protective effect in the 2K1C hypertensive rats.

Garcinia dulcis Extract Alleviates Inflammation in Kidney and Liver of the 2-Kidney-1-Clip Hypertensive rat

Garcinia dulcis (GD) extract possesses anti-hypertensive property that are poorly characterized. This study aimed to investigate an anti-inflammatory effect of GD flower extract in the 2-kidney-1-clip (2K1C) hypertensive compared to sham operative (SO) rat. Male Wistar rats were divided into 2 groups; the 2K1C group in which a silver clip was placed around renal artery to induce hypertension, and the SO normotensive group. Four weeks later, each group of rats were further divided into 2 subgroups, each subgroup was orally gavaged of either corn oil (vehicle) or 50 mg/kg BW GD extract daily for 4 weeks. The malondialdehyde (MDA) levels in serum, liver, and kidney were determined. Hematoxylin and eosin staining was carried out for histological examination, Periodic acid - Schiff staining for glomerular injury, Masson's trichrome staining for renal fibrosis, and immunohistochemistry for either tumor necrosis factor alpha (TNF-α) or endothelial nitric oxide synthase (eNOS) investigation. Taken together, our results demonstrated that GD flower extract decreased the MDA level in both serum and liver and kidney tissue and suppressed the expression of TNF-α in both liver and kidney of 2K1C hypertensive rats. Mesangial cell proliferation, expansion of mesangial matrix, widening Bowman's capsule space, congestion of glomerular capillary and vessel, cloudy swelling of renal tubular epithelial cell, and renal fibrosis were observed in the kidneys of 2K1C rats. Therefore, we concluded that GD flower extract can alleviate liver and kidney inflammation in which partially attenuates the glomerular injury in the 2K1C rat.

Inhibitory mechanisms of promising antimicrobials from plant byproducts: A review

Plant byproducts and waste present enormous environmental challenges and an opportunity for valorization and industrial application. Due to consumer demands for natural compounds, the evident paucity of novel antimicrobial agents against foodborne pathogens, and the urgent need to improve the arsenal against infectious diseases and antimicrobial resistance (AMR), plant byproduct compounds have attracted significant research interest. Emerging research highlighted their promising antimicrobial activity, yet the inhibitory mechanisms remain largely unexplored. Therefore, this review summarizes the overall research on the antimicrobial activity and inhibitory mechanisms of plant byproduct compounds. A total of 315 natural antimicrobials from plant byproducts, totaling 1338 minimum inhibitory concentrations (MIC) (in μg/mL) against a broad spectrum of bacteria, were identified, and a particular emphasis was given to compounds with high or good antimicrobial activity (typically <100 μg/mL MIC). Moreover, the antimicrobial mechanisms, particularly against bacterial pathogens, were discussed in-depth, summarizing the latest research on using natural compounds to combat pathogenic microorganisms and AMR. Furthermore, safety concerns, relevant legislation, consumer perspective, and current gaps in the valorization of plant byproducts-derived compounds were comprehensively discussed. This comprehensive review covering up-to-date information on antimicrobial activity and mechanisms represents a powerful tool for screening and selecting the most promising plant byproduct compounds and sources for developing novel antimicrobial agents.

Anti-Inflammatory Effect of Garcinol Extracted from Garcinia dulcis via Modulating NF-κB Signaling Pathway

Garcinia is a significant medicinal plant with many beneficial phytoconstituents, including garcinol. This study investigated the anti-inflammatory effect of garcinol isolated from Garcinia dulcis fruit in LPS-activated THP-1 and Raw 264.7 macrophages. The results demonstrated that the low concentration of garcinol did not alter cell viability. Furthermore, co-incubation of garcinol with LPS inhibited the production of pro-inflammatory cytokines, including TNF-α, IL-8, IL-6, IL-1β, and pro-inflammatory mediators, including iNOS and COX-2 at the mRNA and protein expression levels. Garcinol also decreased the secretion of TNF-α, IL-6, IL-1β, PGE2, and NO. Moreover, the anti-inflammatory effects involved an alteration in the NF-κB signaling pathway. Downregulation of pIKKα/β, pIκBα, and pNF-κB was observed, hence reducing the translocation of pNF-κB from the cytosol into the nucleus, which subsequently decreased the production of pro-inflammatory molecules. Therefore, garcinol isolated from Garcinia dulcis is a potential candidate as an anti-inflammatory agent for inflammation-related disease treatment.

Camboginol and Morelloflavone from Garcinia dulcis (Roxb.) Kurz Flower Extract Promote Autophagic Cell Death against Human Glioblastoma Cells through Endoplasmic Reticulum Stress

Garcinia dulcis is a tropical plant native to Southeast Asia that is traditionally used as a folk remedy to cure several pathological symptoms. Camboginol and morelloflavone have been revealed by previous studies as the principal bioactive compounds from the flower extract of G. dulcis. The disease-preventing properties of camboginol or morelloflavone, including anti-cancer, from various parts of G. dulcis have been revealed by recent studies. Glioblastoma is the aggressive malignant stage of brain cancer and suffers from chemotherapeutic resistance. This study aimed to test the anti-cancer effect of G. dulcis flower extract against the proliferation of A172 human glioblastoma cells. The extract had cytotoxic activity and promoted cell cycle arrest at the S and G2/M phases. Autophagic cell death was promoted by cytotoxic concentrations of the extract, as observed by enhancing autophagic flux and the expression of autophagic markers. Autophagic cell death induced by the extract might be associated with endoplasmic reticulum (ER) stress. Conclusively, it was indicated by this study that the extract from the flower of G. dulcis had a protective effect against the proliferation of A172 human glioblastoma cells through the induction of ER stress-mediated cytotoxic autophagy.

First report on phytochemical investigation, antioxidant and antidiabetic activities of Helianthemum getulum

A new flavonoid, 5,7,2',4',5'-pentahydroxyflavone 3-O-β-D-galactopyranoside (12) and twelve known derivatives: an aryltetralin-lignan (3), seven flavonoids (4-5, 7-10, 13) and four phenolic acids (1-2, 6, 11) have been isolated from the aerial parts of Helianthemum getulum Pomel. (Cistaceae family) an endemic species to the septentrional Sahara that is being studied for the first time. Structure elucidation of the isolated compounds was established by means of spectroscopic methods especially NMR and Mass Spectrometry. In vitro antioxidant (DPPH, ABTS, GOR and CUPRAC assays) and antidiabetic (micro-dilution method) activities of the crude extract, fractions and isolated compounds were performed. The new flavonol (12) and Compounds (2, 3, 7, 9) were found to be the most active, some of them exhibiting better activity than the antioxidant standards. Compounds 7, 9 and 3 showed higher α-glucosidase inhibitory activity compared to standard acarbose (IC₅₀= 2.70 ± 0.03 µM, 3.09 ± 0.03 µM, 37.28 ± 1.20 µM and 275.43 ± 1.59 µM, respectively).

Rapid characterization of chemical constituents of Platycodon grandiflorum and its adulterant Adenophora stricta by UPLC-QTOF-MS/MS

Platycodon grandiflorum (PG) is extensively used for treating cough, excessive phlegm, sore throat, bronchitis and asthma, whereas Adenophora stricta (AS) is commonly used to reduce phlegm, clear lung and tonify stomach. Due to similar appearances, PG is sometimes adulterated with cheap AS so as to gain profits. And this will inevitably result in different pharmacological property. In order to further clarify the differences in the chemical composition of these two Chinese herbs, the ultra-high performance liquid chromatography combined with quadrupole time-of-flight tandem mass spectrometry coupled with UNIFI platform was used to establish a reliable, simple, sensitive and rapid analytical method. Seventy-five compounds, including triterpenoid saponins, organic acids, flavonoids, steroids, phenols, etc., were identified from PG based on MS^E data and retention time under the optimized conditions. Meanwhile, 57 compounds including triterpenoid saponins, organic acids, steroids, phenols, alkaloids, etc. were identified from AS. Among all the identified compounds, there were only 14 common components (mainly organic acids) existing in two herbs, and most of the other chemical compositions are totally different between the two herbs. Based on the results, AS cannot substitute for PG. In addition, PG adulterated with AS will lead a poor efficacy in clinical application. In addition, the systematic comparison of similarities and differences between two Chinese herbs will provide reliable characterization profiles to clarify the pharmacological fundamental substances.

Phytoconstituents and Biological Activities of Garcinia Dulcis (Clusiaceae): A Review

Garcinia dulcis (Roxb.) Kurz is a tropical fruit tree native to Southeast Asia where it has a long history of use as a traditional medicine for the treatment of ailments such as lymphatitis, parotitis, struma, scurvy, cough, and sore throat. Despite its medicinal values, this plant is not well known and rarely found nowadays. Research on the phytochemical constituents and biological activities of G. dulcis have demonstrated that various parts of the plant contain an abundance of bioactive compounds mainly xanthones and flavonoids, with significant pharmacological properties such as anti-atherosclerosis, anti-bacterial, anti-cancer, anti-hypertension, and anti-malarial. In the present review, current knowledge of the phytochemistry of G. dulcis and biological activities of its active constituents based on the available literature are summarized in order to explore application potentials and prospective research works on this plant.

A Critical Evaluation of the Quality of Published 13C NMR Data in Natural Product Chemistry

Nuclear Magnetic Resonance spectroscopy contributes very efficiently to the structure elucidation process in organic chemistry. Carbon-13 NMR spectroscopy allows direct insight into the skeleton of organic compounds and therefore plays a central role in the structural assignment of natural products. Despite this important contribution, there is no established and well-accepted workflow protocol utilized during the first steps of interpreting spectroscopic data and converting them into structural fragments and then combining them, by considering the given spectroscopic constraints, into a final proposal of structure. The so-called "combinatorial explosion" in the process of structure generation allows in many cases the generation of reasonable alternatives, which are usually ignored during manual interpretation of the measured data leading ultimately to a large number of structural revisions. Furthermore, even when the determined structure is correct, problems may exist such as assignment errors, ignoring chemical shift values, or assigning lines of impurities to the compound under consideration. An extremely large heterogeneity in the presentation of carbon NMR data can be observed, but, as a result of the efficiency and precision of spectrum prediction, the published data can be analyzed in substantial detail.This contribution presents a comprehensive analysis of frequently occurring errors with respect to ¹³C NMR spectroscopic data and proposes a straightforward protocol to eliminate a high percentage of the most obvious errors. The procedure discussed can be integrated readily into the processes of submission and peer-reviewing of manuscripts.

A new furanoxanthone from Garcinia mangostana

Our phytochemical study on the stem bark of Garcinia mangostana has led to the discovery of a new furanoxanthone, mangaxanthone A (1), together with five known analogs. The five known analogs that were isolated are α-mangostin (2), β-mangostin (3), cowagarcinone B (4), and dulcisxanthone F (5). The structural elucidations of these compounds were carried out by interpreting their spectroscopic data, mainly 1D and 2D NMR spectra and MS.

New secondary metabolites from bioactive extracts of the fungus Armillaria tabescens

Ethyl acetate extracts of Armillaria tabescens (strain JNB-OZ344) showed significant fungistatic and bacteristatic activities against several major human pathogens including Candida albicans, Cryptococcus neoformans, Escherichia coli and Mycobacterium intracellulare. Chemical analysis of these extracts led to the isolation and identification of four new compounds, emestrin-F (1), emestrin-G (2), 6-O-(4-O-methyl-β-D-glucopyranosyl)-8-hydroxy-2,7-dimethyl-4H-benzopyran-4-one (3) and cephalosporolide-J (4), along with five other previously known compounds, emestrin (5), cephalosporolide-E (6), decarestrictine-C2 (7), ergosterol and brassicasterol. Structural elucidation of all compounds was carried out by NMR and MS analyses. Antimicrobial assays revealed that compounds 1 and 5 were responsible for the observed growth inhibitory activities of the fungal extracts against the human pathogens tested.

Concise Approach to 1,4-Dioxygenated Xanthones via Novel Application of the Moore Rearrangement

The rapid synthesis of 1,4-dioxygenated xanthones and related natural products employing the Moore rearrangement as a key transformation has been developed. The approach features an acetylide stitching step to unite a substituted squaric acid with a protected hydroxy benzaldehyde derivative to provide a key intermediate that undergoes facile Moore rearrangement to deliver a hydroxymethyl aryl quinone. Subsequent oxidation, hydroxy group deprotection and cyclization then affords highly functionalized xanthones. The utility of the approach was demonstrated by its application to a concise and efficient synthesis of the naturally-occurring xanthone 1. The structure of a natural product that had been named dulcisxanthone C was also corrected to that of the xanthone 1.

Genotoxicity assessment of Garcinia achachairu Rusby (Clusiaceae) extract in mammalian cells in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Garcinia achachairu Rusby (Clusiaceae) is popularly known as "achachairu", and is used in Bolivian folk medicine for its healing, digestive, and laxative properties, and in the treatment of gastritis, rheumatism and inflammation. Despite its widespread therapeutic use, there is a lack of data regarding its in vivo genotoxic effects. Therefore, in this study, we used the comet assay and the micronucleus test, respectively, to evaluate the possible genotoxic and clastogenic effects of Garcinia achachairu seed extract (GAE) on different cells of mice.

MATERIAL AND METHODS

The GAE was administered by oral gavage at doses of 500, 1000 and 2000 mg/kg. For the analysis, the comet assay was performed on the leukocytes (collected 4 and 24 h after treatment), liver, bone marrow and testicular cells (collected 24 h after treatment), and the micronucleus test (MN) on bone marrow cells. Cytotoxicity was assessed by scoring 200 consecutive polychromatic (PCE) and normochromatic (NCE) erythrocytes (PCE/NCE ratio).

RESULTS AND CONCLUSION

The results showed that GAE did not induce significant DNA damage in leukocytes (4 h and 24 h samples), liver, bone marrow and testicular cells (24 h samples). GAE also did not show any significant increase in micronucleated polychromatic erythrocytes (MNPCEs) at the three tested doses. The PCE/NCE ratio indicated no cytotoxicity. Under our experimental conditions, the data obtained suggest that a single oral administration of G. achachairu extract does not cause genotoxicity and clastogenicity in different cells of mice.

Morelloflavone, a biflavonoid inhibitor of migration-related kinases, ameliorates atherosclerosis in mice

While macrophages take up modified LDL to form foam cells and multiply to develop fatty streaks, vascular smooth muscle cells (VSMC) migrate from the media to intima, secrete extracellular matrix, and increase the volume of atherosclerotic lesions. A medicinal plant Garcinia dulcis has been used in traditional Thai medicine for centuries to treat various chronic human diseases. Morelloflavone, a biflavonoid and an active ingredient of the plant, has been shown to inhibit VSMC migration through its inhibition of multiple migration-related kinases such as focal adhesion kinase, c-Src, ERK, and RhoA. However, the exact role of morelloflavone in atherosclerogenesis was unknown. We fed Ldlr(-/-)Apobec1(-/-) mice with either normal chow or chow containing 0.003% morelloflavone for 8 mo and assessed the extent of atherosclerosis by the en face and cross-sectional analyses. A cell composition analysis of atherosclerotic tissue was carried out using immunohistochemical staining. Oral morelloflavone therapy significantly reduced the atherosclerotic areas of the mouse aortas (a 26% reduction), without changing plasma lipid profiles or weights. Immunohistochemical analyses showed that morelloflavone reduced the number of VSMC in the atherosclerotic lesion while it did not change the density of macrophages in the lesion or the percentages of proliferating and apoptotic cells. Oral, low-dose, morelloflavone therapy retards atherosclerogenesis by limiting the migration of VSMC into the intima in the mouse model of human atherosclerosis. Upon further investigation, morelloflavone may be found to be a novel oral antiatherosclerotic agent and a viable addition to the conventional therapies such as statins in humans.

General and expedient synthesis of 1,4-dioxygenated xanthones

A facile entry to 1,4-dioxygenated xanthones having a variety of substitution patterns and substituents was developed that features a novel application of the Moore cyclization using substrates that were readily assembled in a highly convergent fashion by an acetylide stitching process. The practical utility of the methodology was demonstrated by an efficient synthesis of a naturally occurring xanthone and correction of the structure of dulcisxanthone C.

Morelloflavone from Garcinia dulcis as a novel biflavonoid inhibitor of HMG-CoA reductase

Morelloflavone, a biflavonoid from Garcinia dulcis previously shown to have hypocholesterolemic activity, was examined for its effect on HMG-CoA reductase, the rate-limiting enzyme of the cholesterol biosynthetic pathway. By using the catalytic domain of house mouse HMG-CoA reductase, morelloflavone was found to inhibit the enzyme activity by competing with HMG-CoA whereas it was non-competitive towards NADPH. The inhibition constants (K(i)) with respect to HMG-CoA and NADPH were 80.87 ± 0.06 µm and 103 ± 0.07 µm, respectively. Both flavonoid subunits of this compound, naringenin and luteolin, equally competed with HMG-CoA with K(i) of 83.58 ± 4.37 µm and 83.59 ± 0.94 µm, respectively, and were also non-competitive with NADPH (K(i) of 182 ± 0.67 µm and 188 ± 0.14 µm, respectively). Due to these findings, we suggest that each subunit of morelloflavone would occupy the active site of the enzyme, thereby blocking access of its substrate. The present study thus demonstrates the ability of morelloflavone from G. dulcis to inhibit HMG-CoA reductase in vitro. As a result, this biflavonoid might serve as a new candidate for the future development of hypocholesterolemic agents.

Chromene and prenylated xanthones from the roots of Cratoxylum formosum ssp. pruniflorum

Two new xanthones, namely pruniflorone K (1) and L (2), have been isolated from the roots of Cratoxylum formosum ssp. pruniflorum, along with thirteen known xanthones (3-15). Their structures were mainly established using the spectroscopic methods. Only isolated compounds with sufficient amount were evaluated for antibacterial and antifungal activities.

Antimalarial compounds from the root bark of Garcinia polyantha Olv

Eight compounds were isolated from the roots of Garcinia polyantha, and identified. Two of them, the xanthone garciniaxanthone I (1), and the triterpene, named garcinane (2), are reported as new natural products. The structures of the new compounds were elucidated on the basis of 1D and 2D NMR spectroscopic studies. The structure of compound 1 was confirmed by X-ray crystallography. Among the remaining six known compounds, three were known xanthones [smeathxanthone A (3), smeathxanthone B (4), and chefouxanthone (5)], one benzophenone [isoxanthochymol (6)], one triterpene [magnificol], and one sterol [beta-sitosterol]. The in vitro antimalarial activity of isoxanthochymol (6) against Plasmodium falciparum shows strong chemosuppression of parasitic growth.

Morelloflavone blocks injury-induced neointimal formation by inhibiting vascular smooth muscle cell migration

BACKGROUND

In-stent restenosis, or renarrowing within a coronary stent, is the most ominous complication of percutaneous coronary intervention, caused by vascular smooth muscle cell (VSMC) migration into and proliferation in the intima. Although drug-eluting stents reduce restenosis, they delay the tissue healing of the injured arteries. No promising alternative anti-restenosis treatments are currently on the horizon.

METHODS

In endothelium-denudated mouse carotid arteries, oral morelloflavone-an active ingredient of the Thai medicinal plant Garcinia dulcis-significantly decreased the degree of neointimal hyperplasia, without affecting neointimal cell cycle progression or apoptosis as evaluated by Ki-67 and TUNEL staining, respectively. At the cellular level, morelloflavone robustly inhibited VSMC migration as shown by both scratch wound and invasion assays. In addition, morelloflavone prevented VSMCs from forming lamellipodia, a VSMC migration apparatus. Mechanistically, the inhibition by morelloflavone of VSMC migration was through its negative regulatory effects on several migration-related kinases, including FAK, Src, ERK, and RhoA. Consistently with the animal data, morelloflavone did not affect VSMC cell cycle progression or induce apoptosis.

RESULTS

These data suggest that morelloflavone blocks injury-induced neointimal hyperplasia via the inhibition of VSMC migration, without inducing apoptosis or cell cycle arrest.

GENERAL SIGNIFICANCE

We propose morelloflavone to be a viable oral agent for the prevention of restenosis, without compromising effects on the integrity and healing of the injured arteries.

Polyanxanthone A, B and C, three xanthones from the wood trunk of Garcinia polyantha Oliv

Three xanthones, polyanxanthone A (1), B (2) and C (3) have been isolated from the methanol extract of the wood trunk of Garcinia polyantha, along with five known xanthones: 1,3,5-trihydroxyxanthone (4); 1,5-dihydroxyxanthone (5); 1,3,6,7-tetrahydroxyxanthone (6); 1,6-dihydroxy-5-methoxyxanthone (7) and 1,3,5,6-tetrahydroxyxanthone (8). Their structures were determined by means of 1D- and 2D-NMR techniques. Some of the above compounds were screened for their anticholinesterase activity on acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes.

Synthesis of unnatural flavonoids and stilbenes by exploiting the plant biosynthetic pathway in Escherichia coli

Flavonoids and stilbenes have attracted much attention as potential targets for nutraceuticals, cosmetics, and pharmaceuticals. We have developed a system for producing "unnatural" flavonoids and stilbenes in Escherichia coli. The artificial biosynthetic pathway included three steps. These included a substrate synthesis step for CoA esters synthesis from carboxylic acids by 4-coumarate:CoA ligase, a polyketide synthesis step for conversion of the CoA esters into flavanones by chalcone synthase and chalcone isomerase, and into stilbenes by stilbene synthase, and a modification step for modification of the flavanones by flavone synthase, flavanone 3beta-hydroxylase and flavonol synthase. Incubation of the recombinant E. coli with exogenously supplied carboxylic acids led to production of 87 polyketides, including 36 unnatural flavonoids and stilbenes. This system is promising for construction of a larger library by employing other polyketide synthases and modification enzymes.

Synthesis of Kaempferitrin

A short synthesis of Kaempferitrin (1), a 3,7-diglycosylflavone, is reported. Key features include the synthesis of a protected form of kaempferol in which all four hydroxy groups are differentiated and the first bis-glycosylation of a dihydroxyflavone. This synthesis will allow the preparation of derivatives for further explorations into the origins of this compound's biological activity.