O-Methyl-4-hydroxy mellein

Two Neofusicoccumparvum isolates and a UV mutant were characterized for their phytotoxin production in vitro, their pathogenicity on grapevine, and their genome sequenced. The isolate Np-Bt67 produced high level of (-)-terremutin, but almost no (R)-mellein, and it was the most aggressive on grapevine, triggering apoplexy. Similar symptoms were not induced by purified (-)-terremutin. The isolate Bourgogne S-116 (Np-B) produced 3-fold less (-)-terremutin and high amounts of (R)-mellein, but it was less aggressive on grapevine than Np-Bt67. The UV9 mutant obtained from Np-B (NpB-UV9) no longer produced (-)-terremutin but overproduced (R)-mellein by 2.5-fold, and it was as pathogenic as its parent. NpB-UV9 differed from its parent by simple mutations in two genes (transcription factor UCR-NP2_6692, regulatory protein UCR-NP2_9007), not located neither near (R)-mellein, nor (-)-terremutin biosynthetic genes, but likely involved in the control of (-)-terremutin biosynthesis. Grapevine immunity was disturbed upon challenge with these pathogens or purified phytotoxins, leading to an upregulation of SA-dependent defenses, while (-)-terremutin interfered with host JA/ET-dependent defenses. Our results suggest that neither (-)-terremutin nor (R)-mellein alone is essential for the pathogenicity of N. parvum on grapevine, since isolate/mutant non-producing these toxins in vitro is pathogenic. However, these phytotoxins could play a quantitative role in the infection process.

In an on-going investigation of bioactive metabolites producing potential endophytic fungi, the strain Lasiodiplodia theobromae (SJF-1) was isolated from a medicinal plant Syzygium cumini. The cultural, morphological and molecular identification was done with the SJF-1 strain. The obtained gene sequence was deposited in NCBI with accession number MG 938644. The methanolic extract of SJF-1 strain possessed one major bioactive fraction, and it was purified by column chromatography. Further, it was identified as Mellein by various spectroscopic studies (1 H, 13 C, DEPT-135°, FT-IR, ESI-HR-MS and 2D NMR). Biologically, Mellein showed potent anti-Xanthomonas activity with minimum inhibitory concentration (MIC) values ranging from 1·9 to 62·5 μg ml-1 against 11 Xanthomonas strains, a broad-spectrum antimicrobial activity with MIC 7·8-31·25 μg ml-1 and 1·9-31·25 μg ml-1 towards both bacterial and fungal strains, respectively. The scanning electron microscope analysis proved the antimicrobial efficacy of a Mellein by rupturing the cell walls of Xanthomonas sp. Molecular docking studies further supported that the Mellein showed good binding interactions with the proteins of Xanthomonas sp. to reduce pathogenicity. Further, in silico pharmacological studies showed that this metabolite exhibited high gastrointestinal absorption properties and promising oral drug bioavailability. We report, anti-Xanthomonas, in silico docking and pharmacological studies of Mellein from (SJF-1) strain for the first time.

The phytochemical investigation of crude n-hexane and ethyl acetate extracts from twigs of Afzelia xylocarpa (Kurz) led to the isolation of 14 known compounds. Their structures were elucidated by spectroscopic techniques (IR, 1H NMR, 13C NMR, and 2D NMR) as well as mass spectrometry. These structures were characterized as β-sitosterol (1), lupeol (2), vanilic acid (3), 5,7-dihydroxychromone (4), (+)-mellein (5), isoliquiritigenin (6), 7-hydroxyemodin (7), physion (8), aromadendrin (9), naringenin (10), apigenin (11), luteolin (12), chrysoeriol (13) and kaempferol (14). Compounds 4-7 and 12-13 were isolated from the genus Afzelia for the first time. The selected compounds 5, 8, 9 and 12 exhibited potent activity for antioxidation kinetics of oxymyoglobin.