A kernel nonparametric quantile estimator for right-censored competing risks data

In medical and epidemiological studies, it is often interest to study time-to-event distributions under competing risks that involve two or more failure types. Nonparametric analysis of competing risks is typically focused on the cumulative incidence function or nonparametric quantile function. However, the existing estimators may be very unstable due to their unsmoothness. In this paper, we propose a kernel nonparametric quantile estimator for right-censored competing risks data, which is a smoothed version of Peng and Fine's nonparametric quantile estimator. We establish the Bahadur representation of the proposed estimator. The convergence rate of the remainder term for the proposed estimator is substantially faster than Peng and Fine's quantile estimator. The pointwise confidence intervals and simultaneous confidence bands of the quantile functions are also derived. Simulation studies illustrate the good performance of the proposed estimator. The methodology is demonstrated with two applications of the Supreme Court Judge data and AIDSSI data.</p

Naturally Occurring Asterric Acid Analogs: Chemistry and Biology

Asterric acid and its analogs belong to diphenyl ethers (DPEs) with multiple substitutions on A/B aromatic rings. This member of DPEs originates from the polyketide pathway and displays a wide range of biological effects. Though the structures of asterric acid analogs are not complex, there were only more than 50 asterric acid analogs found in nature from 1960 to 2023. In this review, the structures, bioactivities, and biosynthesis of asterric acid analogs are summarized. More importantly, the empirical rule about the shielding effect of B-ring on H-6 is suggested, and this provides a convenient and useful way to analyze the NMR spectral data of asterric acid analogs, based on which the chemical shift values of the A-ring in some asterric acid analogs are revised

Antifungal Metabolites from the Plant Endophytic Fungus <i>Pestalotiopsis foedan</i>

Pestafolide A (1), a new reduced spiro azaphilone derivative, and pestaphthalides A (2) and B (3), two new isobenzofuranones, have been isolated form solid cultures of an isolate of Pestalotiopsis foedan. The structures of these compounds were determined mainly by analysis of their NMR spectroscopic data. The relative configuration of 1−3 was assigned by analysis of 1H NMR J-values and NOESY data, and the absolute configuration was determined by application of the CD excitation chirality and modified Mosher method. Compounds 1−3 showed modest antifungal activity

Bioactive steroids from seed germination supporting fungus (<i>Ceratobasidium</i> GS2) of the terrestrial orchid <i>Gymnadenia conopsea</i>

Almost all orchids rely on mycorrhizal fungus to support their seed germination. To date, the effect of active components in mycorrhizal fungus on orchid seed germination largely remains unknown. In this study, we aimed to investigate the impact of active components found in mycorrhizal fungus on orchid seed germination. Specifically, we focused on a terrestrial orchid Gymnadenia conopsea and its host-specific seed germination supporting fungus Ceratobasidium GS2. In total, several steroids (1–7) were isolated from this fungus. Notably, compounds 1, 2, 4, and 5 exhibited significant enhancements in protocorm volume. Moreover, compounds 1–6 demonstrated strong promotion of protocorm differentiation. These findings suggest that steroids may play a crucial role in the symbiotic germination of G. conopsea seeds. Future studies should continue to explore the specific mechanisms through which these steroids exert their effects, contributing to our understanding of orchid biology and mycorrhizal interaction.</p

Ambuic Acid and Torreyanic Acid Derivatives from the Endolichenic Fungus <i>Pestalotiopsis</i> sp.

Six new ambuic acid (1) derivatives (2−7) and a new torreyanic acid analogue (8) have been isolated from the crude extract of endophytic fungus Pestalotiopsis sp. inhabiting the lichen Clavaroids sp. The structures of these compounds were elucidated primarily by NMR and MS methods, and their absolute configurations were assigned by application of the CD excitation chirality method. Compounds 1 and 2 displayed antimicrobial activity against the Gram-positive bacterium Staphylococcus aureus

Photinides A−F, Cytotoxic Benzofuranone-Derived γ-Lactones from the Plant Endophytic Fungus <i>Pestalotiopsis photiniae</i>

Photinides A−F (1−6), six new unique benzofuranone-derived γ-lactones, have been isolated from the crude extract of the plant endophytic fungus Pestalotiopsis photiniae. The structures of these compounds were elucidated primarily by NMR spectroscopy, and their absolute configurations were assigned by application of the CD excitation chirality method. Compounds 1−6 displayed modest cytotoxic effects against the human tumor cell line MDA-MB-231

Pestaloquinols A and B, Isoprenylated Epoxyquinols from <i>Pestalotiopsis</i> sp.

Two new isoprenylated epoxyquinol derivatives, pestaloquinols A (2) and B (3), and their putative biosynthetic precursor, cytosporin D (1), were isolated from the crude extract of the plant endophytic fungus Pestalotiopsis sp. The structures of these compounds were elucidated primarily by NMR experiments. Pestaloquinols A (2) and B (3) possess a previously undescribed nonacyclic ring system and showed cytotoxicity against HeLa cells

Pestalazines and Pestalamides, Bioactive Metabolites from the Plant Pathogenic Fungus <i>Pestalotiopsis theae</i>

Pestalazines A (1) and B (2), two new diketopiperazine heterodimers, and pestalamides A−C (3−5), three new amides, have been isolated from cultures of the plant pathogenic fungus Pestalotiopsis theae. The structures of these compounds were elucidated mainly by NMR spectroscopy. The absolute configurations of 1 and 2 were determined using Marfey’s method on their acid hydrolysates and by comparison of their CD spectra with that of a model compound. Compounds 1, 3, and 6 displayed inhibitory effects on HIV-1 replication in C8166 cells. Compound 3 also showed potent antifungal activity against Aspergillus fumigatus

Luteoloside reduced EV71 production.

(A) RD cells grown in 6-well-plate were infected with EV71 (MOI = 0.3) in the presence or absence of 0.5 mM luteoloside. The intercellular and extracellular virions were collected at the indicated time points for plaque reduction assay by freeze-thawing. (B) RD cells were infected with EV71 (MOI = 0.3). 0.5 mM luteoloside were supplemented to infected RD cells according to different protocols (C) respectively. The cell viability was detected using MTS cell proliferation assay kit at 48 hpi. The viability of control group was set as 100%. Data shown are the means ± SE from 6 independent measurements (n = 6). Asterisk meant the data differed from the EV71 group significantly at Pt-test.</p

Data_Sheet_1_Furanoids from the Gymnadenia conopsea (Orchidaceae) seed germination supporting fungus Ceratobasidium sp. (GS2).docx

Five furanoids including a new analog (S)-1,4-di(furan-2-yl)-2-hydroxybutane-1,4-dione (1) together with four known ones, rhizosolaniol (2), 5-hydroxymethylfurfural (3), 2-furoic acid (4) and (2-furyl) oxoacetamide (5), were isolated from the fungal strain Ceratobasidium sp. (GS2) inducing seed germination of the endangered medicinal plant Gymnadenia conopsea of Orchidaceae. The structure of new furanoid 1 was determined mainly based on HR-ESI-MS and NMR spectral data. Modified Mosher’s reactions were used to establish the stereochemistry of the hydroxyl group in 1, which was not stable in Mosher’s reagents and transformed into four analogs 6–9. These degraded products (6–9) were elucidated based on UPLC-Q-TOF-MS/MS analysis, and compound 8 was further isolated from the degraded mixture and its structure was characterized through NMR experiments. Therefore, the absolute configuration of compound 1 was determined by electronic circular dichroism combined with quantum-chemical calculations adopting time-dependent density functional theory. Compounds (1–5), and 8 showed weak antioxidant activities, and compounds (2–4) displayed phytotoxicity on punctured detached green foxtail leaves. In addition, compounds 3 and 4 strongly showed inhibition activities on the seed germination of G. conopsea. This was the first chemical investigation of the symbiotic fungus of G. conopsea.</p