Ascorbic acid in pollen: Conversion of L-galactono-1,4-lactone to L-ascorbic acid by Lilium longiflorum

The L-ascorbic acid (AA) content of pollen from three cultivars of Lilium longiflorum Thunb. was 260–280 μg/g fresh wt. of pollen. During germination ascorbic acid content gradually decreased reaching 70% of the original value at 6 h. Pollen germinated in media containing 0.29 M D-glucose (an osmoregulator and carbon source) failed to synthesize ascorbic acid but pollen germinated in 0.29 M pentaerythritol (a non-metabolizable osmoregulator) supplemented with L-galactono-1,4-lactone (L-GalAL) did form ascorbic acid, dependent upon the concentration of the lactone. Lycorine inhibited germination but had negligible effect on the conversion of L-GalAL to AA.     

Glucosyloxy alkaloids from Pancratium biflorum

From fluids of flower stems and bulbs, and from extracts of roots of Pancratium biflorum, collected at different stages of growth, three new glucosyloxy alkaloids, viz. hordenine-4-O-β-d-glucoside, lycorine-1-O-β-d-glucoside and pseudolycorine-1-O-β-d-glucoside, have been isolated and characterized. Additionally, three proto alkaloids, β-phenethylamine, tyramine and hordenine, together with four true alkaloids, lycorine, pseudolycorine, pretazettine and tazettine, encountered before in other memebrs of the Amaryllidaceae, have now been isolated also from this species. Ontogenic variations of alkaloidal constituents have been observed. The ability of the alkaloidal constituents to complex with divalent metal ions and phytosterols has been examined with a view to evaluating their significance in plant biochemistry.     

Lycorine inhibits melanoma cell migration and metastasis mainly through reducing intracellular levels of β-catenin and matrix metallopeptidase 9

Metastatic melanoma accounts for 60% of death for skin cancer. Although great efforts have been made to treat the disease, effective drugs against metastatic melanoma still lack at the clinical setting. In the current study, we found that lycorine, a small molecule of isoquinoline alkaloid, significantly suppressed melanoma cell migration and invasion in vitro, and decreased the metastasis of melanoma cells to lung tissues in tumor-bearing mice, resulting in significant prolongation of the survival of the mice without obvious toxicity. Molecular mechanistic studies revealed that lycorine significantly reduced intracellular levels of β-catenin protein through degradation of the protein via the ubiquitin–proteasome pathway, and decreased the expression of β-catenin downstream prometastatic matrix metallopeptidase 9 and Axin2 genes. Collectively, our findings support the notion that targeting the oncogenic β-catenin by lycorine is a new option to inhibit melanoma cell metastasis, providing a good drug candidate potential for development novel therapeutics against metastatic melanoma.     

Ascorbate and ascorbate-dependent enzymes in detached tomato leaves under conditions modulating the ascorbate pool

The relationship between AA-metabolising enzymes and the AA pool was studied by subjecting tomato leaves to treatments up- or down-regulating the AA content. GalL feeding through leaf petioles increased the level of cellular ascorbate up to two-fold. This effect accompanied by a AA/total ascorbate ratio increase was observed after a 2-h incubation and remained constant during the following 4 days. Dark-incubated leaves showed a 56% decline in AA content concomitantly with DHA accumulation and significant ascorbate redox ratio decrease. Opposite changes were induced when the darkened leaves were transferred to light, as AA biosynthesis depends on light. The light-induced AA biosynthesis was partially inhibited by lycorine. Regardless of the pattern of AA pool changes the AA-related enzymes were similarly affected. Both the GalL/light-dependent AA increase and dark-induced AA depletion were accompanied by APX and MDHAR activity induction. No significant AA pool-dependent DHAR activity changes were found. The possible relevance of the AA system changes induced is discussed.     

Peptidyltransferase center of ribosomes: On the mechanism of action of alkaloid lycorine

The molecular mechanism of action of the alkaloid lycorine has been revised. According to our results, lycorine inhibits the binding of CACCA-Leu←Ac to the donor site of the peptidyltranferase center of wheat-germ ribosomes, whereas the transpeptidation reaction in the system with the minimal model donor is not inhibited. The equilibrium constant of CACCA-Leu←Ac to the donor site of 80 S ribosomes is measured.     

1H and 13c nmr analysis of lycorine and α-dihydrolycorine

-The ¹H and ¹³C NMR spectra of lycorine and its α-dihydro derivative have been studied. The employment of nuclear magnetic double resonance, nuclear Overhauser effect and acetylated derivatives, allows the assignment of all proton resonances. The assignments of the carbon shifts have been obtained by means of proton noise decoupled, single frequency off-resonance decoupled, single frequency selective decoupling, time dependence nuclear Overhauser effect and by comparison with reference compounds.     

Influence of L-galactonic acid γ -lactone on ascorbate production in some yeasts

L-galactonic acid -lactone appear to influence ascorbic acid production in strains of Saccharomyces cerevisiae, Clavispora lusitaniae, Cryptococcus terreus, Pichia fermentans in which this is undetected whenever glucose represents the sole carbon source. Cryptococcus terreus (strains DBVP 6012 and 6242) does not show ascorbic acid production either in presence or in the absence of L-galactonic acid -lactone. This feature is probably connected to the insensibility of the strain to the lycorine, an alkaloid which commonly inhibits cell division probably by blocking L-galactonic acid -lactone convertion into ascorbate.     

石蒜碱药理活性及构效关系研究进展

石蒜碱是药用石蒜科植物的有效成分之一,是重要的异喹啉类生物碱.石蒜碱拥有刚性的环系骨架、连续的手性中心、三级胺等独特的化学结构特征.同时其药理活性丰富多样,近年来,针对其抗癌、抗病毒、抗炎、抗寄生虫、抑制乙酰胆碱酯酶活性的研究越来越多,尤其在抗癌、抗病毒方面石蒜碱表现出较大潜力,特别是新型冠状病毒SARS-CoV-2研...     

Two non-hydroxylated alkaloids in Crinum augustum

Several alkaloids were isolated from Crinum augustum grown in Assiut, Egypt. Two were identified as lycorine and buphanisine. In addition two new non-hydroxylated alkaloids of identical molecular formula C₁₇H₁₉NO₄ were investigated by spectroscopic methods. The gross structure of the first, termed augustine, belongs to the 1,2-epoxy-5, 10-b-ethanophenanthridine-type. In contrast the second could not be related to any of the known alkaloid types of the Amaryllidaceae.     

Lycorine hydrochloride inhibits metastatic melanoma cell-dominant vasculogenic mimicry

Melanoma cells actively participate in tumor angiogenesis and vasculogenic mimicry. However, anti-angiogenic therapy in patients with melanoma has not shown a significant survival gain. Thus, new anti-melanoma angiogenic and vasculogenic drugs are highly desired. Using the metastatic melanoma cell line C8161 as a model, we explored melanoma vasculogenic inhibitors and found that lycorine hydrochloride (LH) effectively suppressed C8161 cell-dominant formation of capillary-like tubes in vitro and generation of tumor blood vessels in vivo with low toxicity. Mechanistic studies revealed that LH markedly hindered expression of VE-cadherin in C8161 cells, but did not affect expression of six other important angiogenic and vasculogenic genes. Luciferase assays showed that LH significantly impeded promoter activity of the VE-cadherin gene in a dose-dependent manner. Together, these data suggest that LH inhibits melanoma C8161 cell-dominant vasculogenic mimicry by reducing VE-cadherin gene expression and diminishing cell surface exposure of the protein.