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It is commonly accepted that melatonin (N-acetyl-5-methoxytryptamine), the most relevant pineal secretory product, has oncostatic properties in a wide variety of tumors and, especially, in those identified as being hormone-dependent. The objective of the present article is to offer a global and integrative view of the mechanisms involved in the oncostatic actions of this indoleamine. Due to the wide spectrum of melatonins actions, the mechanisms that may be involved in its ability to counteract tumor growth are varied. These include: a) antioxidant effects; b) regulation of the estrogen receptor expression and transactivation; c) modulation of the enzymes involved in the local synthesis of estrogens; d) modulation of cell cycle and induction of apoptosis; e) inhibition of telomerase activity; f) inhibition of metastasis; g) prevention of circadian disruption; h) antiangiogenesis; i) epigenetic effects; j) stimulation of cell differentiation; and k) activation of the immune system. The data supporting each of these oncostatic actions of melatonin are summarized in this review. Moreover, the list of actions described may not be exhaustive in terms of how melatonin modulates tumor growth.

Two new benzojfluoranthene-based secondary metabolites named daldinone C (1) and daldinone D (2), along with two known metabolites, altechromone A and (4S)-5,8-dihydroxy-4-methoxy--tetralone, were isolated from the CHCl3/MeOH (1:1) extract of a solid culture of the endophyte Hypoxylon truncatumIFB-18 harbored inside the symptomless stem tissue of Artemisia annua. The structures of the new compounds were elucidated by MS and 1D and 2D NMR spectra and by X-ray diffraction analysis. Their absolute configurations were determined unambiguously by a combination of their CD data and the established exciton chirality rule. Compounds 1and 2were substantially cytotoxic against SW1116 cells, with IC50values of 49.5 and 41.0 M, respectively, comparable to that (37.0 M) of 5-fluorouracil. The biosynthetic pathway for 1and 2was postulated with the natural occurrence of benzojfluoranthene analogues discussed in brief.

Chaetominine (1), an alkaloidal metabolite with a new framework, was characterized from the solid-substrate culture of Chaetomiumsp. IFB-E015, an endophytic fungus on the apparently healthy Adenophora axillifloraleaves. Its structure was determined by a combination of its spectral data and single-crystal X-ray diffraction analysis, with its absolute configuration elucidated by Marfey's method. Chaetominine was more cytotoxic than 5-fluorouracil against the human leukemia K562 and colon cancer SW1116 cell lines.

Fractionation of the ethanol extract of Palhinhaea cernuaafforded a new (1) and two known p-coumaroylated apigenin glycosides (2, 3) in addition to dillenetin, rhamnazin, -onocerin, -sitosterol, and (E)-2-hydroxy-5-methoxycinnamic acid. The structure of compound 1was elucidated as apigenin-4‘-O-(2‘ ‘-O-p-coumaroyl)--d-glucopyranoside by a combination of its spectroscopic data. The new glycoside 1inhibits xanthine oxidase (IC50:  23.95 ± 0.43 M) in a competitive−noncompetitive manner with Kiand KIvalues of 14.35 and 93.68 M, whereas compounds 2and 3 were inactive. The distribution and significance of acylated flavonoid glycosides are discussed.

A new cytotoxic cytochalasan-based alkaloid named chaetoglobosin U (1), along with four known analogues, chaetoglobosins C (2), F (3), and E (5) and penochalasin A (4), has been characterized from the EtOAc extract of a solid culture of Chaetomium globosum IFB-E019, an endophytic fungus residing inside the stem of healthy Imperata cylindrica. The structure of chaetoglobosin U was determined through correlative analyses of its UV, IR, CD, MS, and 1D (1H and13C NMR and DEPT) and 2D NMR (COSY, NOESY, HMQC, and HMBC) data. Chaetoglobosin U (1) exhibited cytotoxic activity against the human nasopharyngeal epidermoid tumor KB cell line with an IC50 value of 16.0 μM, comparable to that (14.0 μM) of 5-fluorouracil co-assayed as a positive reference. The known analogues 2−5 were moderately active to the cell line, with IC50 values of 34.0, 52.0, 48.0, and 40.0 μM, respectively.