Dihydrochalcones with radical scavenging properties from the leaves ofSyzygium jambos

The Phytotoxin Myrigalone A Triggers a Phased Detoxification Programme and Inhibits Lepidium sativum Seed Germination via Multiple Mechanisms including Interference with Auxin Homeostasis

Molecular responses of plants to natural phytotoxins comprise more general and compound-specific mechanisms. How phytotoxic chalcones and other flavonoids inhibit seedling growth was widely studied, but how they interfere with seed germination is largely unknown. The dihydrochalcone and putative allelochemical myrigalone A (MyA) inhibits seed germination and seedling growth. Transcriptome (RNAseq) and hormone analyses of Lepidium sativum seed responses to MyA were compared to other bioactive and inactive compounds. MyA treatment of imbibed seeds triggered the phased induction of a detoxification programme, altered gibberellin, cis-(+)-12-oxophytodienoic acid and jasmonate metabolism, and affected the expression of hormone transporter genes. The MyA-mediated inhibition involved interference with the antioxidant system, oxidative signalling, aquaporins and water uptake, but not uncoupling of oxidative phosphorylation or p-hydroxyphenylpyruvate dioxygenase expression/activity. MyA specifically affected the expression of auxin-related signalling genes, and various transporter genes, including for auxin transport (PIN7, ABCG37, ABCG4, WAT1). Responses to auxin-specific inhibitors further supported the conclusion that MyA interferes with auxin homeostasis during seed germination. Comparative analysis of MyA and other phytotoxins revealed differences in the specific regulatory mechanisms and auxin transporter genes targeted to interfere with auxin homestasis. We conclude that MyA exerts its phytotoxic activity by multiple auxin-dependent and independent molecular mechanisms.

Syzygium jambos L. Alston: An Insight Into its Phytochemistry, Traditional Uses, and Pharmacological Properties

Medicinal plants have been used since ancient times for human healthcare as drugs, spices, and food additives. The progress in technology and medicine observed, the last decades, has improved the quality of life and healthcare but with worrisome drawbacks. Side effects caused by synthetic drugs for instance originate sometimes irreversible health disorders. Natural substances, in contrast, are biologically and environmentally friendly. Syzygium jambos L. (Alston) also known as rose apple conveys a long history as essential traditional medicine with a broad spectrum of application in various cultures. The plant discloses a diverse group of secondary metabolites and extracts that displayed major susceptibilities towards various health concerns especially stress-related and inflammatory diseases. Despite a rich literature about the plant, the chemistry and biology of S. jambos have not been comprehensively reviewed yet. Accordingly, we present herein a literature survey of rose apple which aims to draw the chemical identity of the plant and establish a consistent discussion on the respective biological application of plant extracts and their corresponding traditional uses. The present work could provide a scientific basis for future studies and necessary information for further investigations of new drug discovery.

Dimeric Acylphloroglucinol Derivatives with New Skeletons from Leptospermum scoparium

Leptosparones A-F (1-6), six new dimeric acylphloroglucinol derivatives with unprecedented skeletons, were isolated from Leptospermum scoparium. Compounds 1-3 and 5-6 are phenylpropanoyl-phloroglucinol dimers, while 4 is a phenylpropanoylphloroglucinol-isovalerylphloroglucinol hybrid. Structurally, these compounds represent the first examples of dimeric phloroglucinols with unprecedented C(7')-C(8) linkage between the phloroglucinol core and the acyl side chain. Their structures were elucidated by comprehensive analyses of spectroscopic data, single crystal X-ray diffraction and chemical calculations. In addition, all compounds showed inhibitory effects against α-glucosidase with IC₅₀ values ranging from 39.5 to 186.8 μM.

Antioxidant activity and mechanism of dihydrochalcone C-glycosides: Effects of C-glycosylation and hydroxyl groups

Dihydrochalcones (DHCs), an important subgroup of flavonoids, have recently received much attention due to their diverse biological activities. In contrast to their O-glycosides, understanding of the antioxidant property and mechanism of DHC C-glycosides remains limited. Herein, the free radical scavenging activity and mechanism of two representative C-glycosyl DHCs, aspalathin (ASP) and nothofagin (NOT) as well as their aglycones, 3-hydroxyphloretin (HPHL) and phloretin (PHL) were evaluated using the density functional theory (DFT) calculations. The results revealed the crucial role of sugar moiety on the conformation and the activity. The o-dihydroxyl in the B-ring and the 2',6'-dihydroxyacetophenone moiety were found significant in determining the activity. Our results showed that hydrogen atom transfer (HAT) is the dominant mechanism for radical-trapping in the gas and benzene phases, while the sequential proton loss electron transfer (SPLET) is more preferable in the polar environments. Also, the results revealed the feasibility of the double HAT and double SPLET as well as the SPLHAT mechanisms, which provide alternative pathways to trap radical for the studied DHCs. These results could deepen the understanding of the antiradical activity and mechanism of DHCs, which will facilitate the design of novel efficient antioxidants.

Leaves of Eugenia brasiliensis Used as a Folk Medicine Contain Cyclooxygenase Enzyme and Lipid Peroxidation Inhibitory Compounds

Tea prepared from leaves of Eugenia brasiliensis has been used as a folk medicine in Brazil to alleviate inflammation and pain. In this study, tea and methanolic extract inhibited cyclooxygenase (COX-1 and -2) enzymes and lipid peroxidation (LPO). Therefore, bioassay-guided purification of methanolic extract was carried out and afforded a new lignan ( aR,8S,8'R-7,8,7’,8'-tetrahydro-8,8'-dimethyl-3,3'-dimethoxy-4,4'-dihydroxy-dibenzocyclooctadiene) and three known C-methylated flavonoids (stropopinin; demethoxymatteucinol; myrigalone G). All isolates at 37.5 μg/mL inhibited COX enzymes, similar to aspirin and ibuprofen used as controls at 108 and 12 μg/mL, respectively. Most of the isolates also showed strong LPO inhibition at 5μg/mL.

Four new cinnamoyl-phloroglucinols from the leaves of Xanthostemon chrysanthus

Four new cinnamoyl-phloroglucinols (1-4) were isolated from the leaves of Xanthostemon chrysanthus. Compounds 1 and 2 represent the first example of natural phloroglucinols with an oxazole unit. Their structures were elucidated on the basis of NMR spectroscopic data and single crystal X-ray diffraction. Compound 3 showed moderate cytotoxic activity against MDA-MB-231 and SGC-7901 cells with IC₅₀ values of 25.26 ± 0.35 μM and 31.2 ± 0.94 μM, respectively.

New Biflavonoids with α-Glucosidase and Pancreatic Lipase Inhibitory Activities from Boesenbergia rotunda

Roots of Boesenbergia rotunda (L.) Mansf. are prominent ingredients in the cuisine of several Asian countries, including Thailand, Malaysia, Indonesia, India, and China. An extract prepared from the roots of this plant showed strong inhibitory activity against enzymes α-glucosidase and pancreatic lipase and was subjected to chromatographic separation to identify the active components. Three new biflavonoids of the flavanone-chalcone type (9, 12, and 13) were isolated, along with 12 known compounds. Among the 15 isolates, the three new compounds showed stronger inhibitory activity against α-glucosidase than the drug acarbose but displayed lower pancreatic lipase inhibitory effect than the drug orlistat. The results indicated the potential of B. rotunda roots as a functional food for controlling after-meal blood glucose levels.

Antimalarial silver and gold nanoparticles: Green synthesis, characterization and in vitro study

In the present study, we are reporting antimalarial potential of silver (AgNPs) and gold (AuNPs) nanoparticles synthesized by leaf and bark extract of Syzygium jambos (L.) Alston (Myrtaceae). AuNPs and AgNPs obtained by both the extracts were characterized using UV-vis spectroscopy, zeta potential, transmission electron microscopy (TEM), X-ray diffraction (XRD), and Fourier Transform Infrared spectroscopy (FTIR). NMR and FTIR spectra indicate that the saccharides and phenolics present in the S. jambos extracts were the major contributors responsible for the synthesis and stabilization of NPs. NPs were also synthesized by chemical methods and were compared for their antiplasmodial potential against chloroquine sensitive (3D7) and resistant (Dd2) strain of Plasmodium falciparum by using 24h schizont maturation assay. AgNPs synthesized by both the extracts showed higher antiplasmodial activity than the rest. Further, NPs synthesized by S. jambos extracts have shown insignificant cytotoxicity against human cervical cancer cell line (HeLa) and rat skeletal muscle cell line (L6), which proved their biocompatibility.

New Phloroglucinol Derivatives from the Fruit Tree Syzygium jambos and Their Cytotoxic and Antioxidant Activities

Seven new phloroglucinol derivatives (1-7) were isolated from the fruit tree Syzygium jambos together with four known triterpenoids (8-11) and two known flavones (12 and 13). According to the spectroscopic analyses (infrared, electrospray ionization mass spectrometry (ESIMS), high-resolution ESIMS, 1D and 2D nuclear magnetic resonance), the structures of compounds 1-7 were elucidated as jambone A (1), jambone B (2), jambone C (3), jambone D (4), jambone E (5), jambone F (6), and jambone G (7). All the isolates were determined for their cytotoxic activities on melanoma cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and compounds 10 and 11 showed potent activities. Moreover, compounds 1, 2, 4-7, 12, and 13 exhibited weak antioxidant activities under ferric-reducing antioxidant power and 2,2-diphenyl-1-picryhydrazyl radical-scavenging assays.

Phytochemical Analyses and Gastroprotective Effects of Eugenia Umbelliflora (Myrtaceae) on Experimental Gastric Ulcers

Phytochemical studies of Eugenia umbelliflora Berg. (Myrtaceae) resulted in the isolation of: taraxerol, α-amyrin, β-amyrin, betulin and betulinic acid from the leaves, as well as trimethoxy ellagic acid from the fruits. Given that several triterpenes were found in the extracts, and that these possess gastroprotective activity, the gastroprotective activity of E. umbelliflora leaf extract was evaluated using ethanol, indomethacin, and stress-induced ulcer models in mice. The crude methanol extract was administrated (v.o) in doses of 50, 125 and 250 mg/kg. The results showed that E. umbelliflora leaves display gastroprotective activity, as demonstrated by significant inhibition of ulcer formation in the different models. The results suggest that the gastroprotective activity may be attributed, at least in part, to the triterpenes.