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Thirty-nine fungal metabolites 1−39, including two new alkaloids, 12β-hydroxy-13α-methoxyverruculogen TR-2 (6) and 3-hydroxyfumiquinazoline A (16), were isolated from the fermentation broth of Aspergillus f umigatus LN-4, an endophytic fungus isolated from the stem bark of Melia azedarach. Their structures were elucidated on the basis of detailed spectroscopic analysis (mass spectrometry and one-and two-dimensional NMR experiments) and by comparison of their NMR data with those reported in the literature. These isolated compounds were evaluated for in vitro antifungal activities against some phytopathogenic fungi, toxicity against brine shrimps, and antifeedant activities against armyworm larvae (Mythimna separata Walker). Among them, sixteen compounds showed potent antifungal activities against phytopathogenic fungi (Botrytis cinerea, Alternaria solani, Alternaria alternata, Colletotrichum gloeosporioides, Fusarium solani, Fusarium oxysporum f. sp. niveum, Fusarium oxysporum f. sp. vasinfectum, and Gibberella saubinettii), and four of them, 12β-hydroxy-13α-methoxyverruculogen TR-2 (6), fumitremorgin B (7), verruculogen (8), and helvolic acid (39), exhibited antifungal activities with MIC values of 6.25−50 μg/ mL, which were comparable to the two positive controls carbendazim and hymexazol. In addition, of eighteen that exerted moderate lethality toward brine shrimps, compounds 7 and 8 both showed significant toxicities with median lethal concentration (LC 50 ) values of 13.6 and 15.8 μg/mL, respectively. Furthermore, among nine metabolites that were found to possess antifeedant activity against armyworm larvae, compounds 7 and 8 gave the best activity with antifeedant indexes (AFI) of 50.0% and 55.0%, respectively. Structure−activity relationships of the metabolites were also discussed.

Two new metabolites, an α-pyridone derivative, 3-hydroxy-2-methoxy-5-methylpyridin-2(1H)-one (1), and a ceramide derivative, 3-hydroxy-N-(1-hydroxy-3-methylpentan-2-yl)-5-oxohexanamide (2), and a new natural product, 3-hydroxy-N-(1-hydroxy-4-methylpentan-2-yl)-5-oxohexanamide (3), along with 15 known compounds including chaetoglobosin C (7) and chaetoglobosin F (8) were isolated from the solid culture of the endophytic fungus Botryosphaeria dothidea KJ-1, collected from the stems of white cedar (Melia azedarach L). The structures were elucidated on the basis of spectroscopic analysis (1D and 2D NMR experiments and by mass spectrometric measurements), and the structure of 1 was confirmed by X-ray single-crystal diffraction. These metabolites were evaluated in vitro for antimicrobial, antioxidant, and cytotoxicity activities. Pycnophorin (4) significantly inhibited the growth of Bacillus subtilis and Staphyloccocus aureus with equal minimum inhibitory concentration (MIC) values of 25 μM. Stemphyperylenol (5) displayed a potent antifungal activity against the plant pathogen Alternaria solani with MIC of 1.57 μM comparable to the commonly used fungicide carbendazim. Both altenusin (9) and djalonensone (10) showed markedly DPPH radical scavenging activities. In addition, stemphyperylenol (5) and altenuene (6) exhibited strong cytotoxicity against HCT116 cancer cell line with a median inhibitory concentration (IC50) value of 3.13 μM in comparison with the positive control etoposide (IC50 = 2.13 μM). This is the first report of the isolation of these compounds from the endophytic B. dothidea.

Chemical functionalization of silicon oxide (SiO(2)) surfaces with silane molecules is an important technique for a variety of device and sensor applications. Quality control of self-assembled monolayers (SAMs) is difficult to achieve because of the lack of a direct measure for newly formed interfacial Si-O bonds. Herein we report a sensitive measure of the bonding interface between the SAM and SiO(2), whereby the longitudinal optical (LO) phonon mode of SiO(2) provides a high level of selectivity for the characterization of newly formed interfacial bonds. The intensity and spectral position of the LO peak, observed upon silanization of a variety of silane molecules, are shown to be reliable fingerprints of formation of interfacial bonds that effectively extend the Si-O network after SAM formation. While the IR absorption intensities of functional groups (e.g., >C=O, CH(2)/CH(3)) depend on the nature of the films, the blue-shift and intensity increase of the LO phonon mode are common to all silane molecules investigated and their magnitude is associated with the creation of interfacial bonds only. Moreover, results from this study demonstrate the ability of the LO phonon mode to analyze the silanization kinetics of SiO(2) surfaces, which provides mechanistic insights on the self-assembly process to help achieve a stable and high quality SAM.

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