H Damianakos

Antimicrobial and Cytotoxic Isohexenylnaphthazarins from Arnebia euchroma (Royle) Jonst. (Boraginaceae) Callus and Cell Suspension Culture

The phytochemical investigation of the n-hexane extract from callus and cell suspension culture of Arnebia euchroma (Royle) Jonst. resulted in the isolation of nine isohexenylnaphthazarins: deoxyalkannin (1), alkannin (2), acetylalkannin (3), isobutyrylalkannin (4), β-hydroxyisovalerylalkannin (5), 2-(S)-α-methylbutyrylalkannin (6), propionylalkannin (7), teracrylalkannin (8) and acetylshikonin (9). Their structures were determined by MS and NMR spectroscopy. Pigments 2–8 are isolated for the first time from Arnebia in vitro cultures, 4 and 7 are reported in the present work as novel metabolites within the Arnebia genus, while 9 is a known constituent of both natural roots and in vitro cultures of A. euchroma. Moreover, methyl jasmonate and 1-monoglyceryl olate, palmitate and stearate are reported for the first time within the Boraginaceae family. The antimicrobial and cytotoxic activities of all isolated pigment compounds were tested, revealing a very interesting profile.

Inhibition of c-MYC with involvement of ERK/JNK/MAPK and AKT pathways as a novel mechanism for shikonin and its derivatives in killing leukemia cells.

Leukemia remains life-threatening despite remarkable advances in chemotherapy. The poor prognosis and drug resistance are challenging treatment. Novel drugs are urgently needed. Shikonin, a natural naphthoquinone, has been previously shown by us to be particularly effective towards various leukemia cell lines compared to solid tumors. However, the underlying mechanisms are still poorly understood. Here, we investigated shikonin and 14 derivatives on U937 leukemia cells. Four derivatives (isobutyrylshikonin, 2-methylbutyrylshikonin, isovalerylshikonin and β,β-dimethylacrylshikonin) were more active than shikonin. AnnexinV-PI analysis revealed that shikonins induced apoptosis. Cell cycle G1/S check point regulation and the transcription factor c-MYC, which plays a vital role in cell cycle regulation and proliferation, were identified as the most commonly down-regulated mechanisms upon treatment with shikonins in mRNA microarray hybridizations. Western blotting and DNA-binding assays confirmed the inhibition of c-MYC expression and transcriptional activity by shikonins. Reduction of c-MYC expression was closely associated with deregulated ERK, JNK MAPK and AKT activity, indicating their involvement in shikonin-triggered c-MYC inactivation. Molecular docking studies revealed that shikonin and its derivatives bind to the same DNA-binding domain of c-MYC as the known c-MYC inhibitors 10058-F4 and 10074-G5. This finding indicates that shikonins bind to c-MYC. The effect of shikonin on U937 cells was confirmed in other leukemia cell lines (Jurkat, Molt4, CCRF-CEM, and multidrug-resistant CEM/ADR5000), where shikonin also inhibited c-MYC expression and influenced phosphorylation of AKT, ERK1/2, and SAPK/JNK. In summary, inhibition of c-MYC and related pathways represents a novel mechanism of shikonin and its derivatives to explain their anti-leukemic activity.

Pyrrolizidine alkaloids from Onosma erecta.

The MeOH extract of the aerial parts of Onosma erecta afforded four new pyrrolizidine alkaloids, 7-O-acetylechinatine N-oxide (1), a viridinatine N-oxide stereoisomer (2), 7-epi-echimiplatine N-oxide (3), and onosmerectine N-oxide (4), and two additional new natural products, the acid 2,3-dimethyl-2,3,4-trihydroxypentanoic acid (5) and the acyloin 4-methyl-2-hydroxypentanone (6).

The chemical profile of pyrrolizidine alkaloids from selected greek endemic boraginaceae plants determined by gas chromatography/mass spectrometry.

Four Greek endemic Boraginaceae plants, Onosma erecta Sibth. & Sm., Onosma kaheirei Teppner, Onosma leptantha Heldr., and Cynoglossum columnae L. (aerial parts), were screened for their content of pyrrolizidine alkaloids (PAs). TLC with the Mattocks-Molyneux visualization reagent was used as a preliminary qualitative test for PA or PA N-oxide detection. The extracts of the species found to contain PAs and their N-oxides were further analyzed by GC/MS, so as to identify their structures by means of the mass spectra and retention index values of known PAs already published in the literature. Twenty-three PAs were identified. For additional peaks, recognized as possible PAs by their MS pattern, no exact structures were tentatively suggested, as a result of lack of matching literature data. Furthermore, a quantitative PA profile of the species was obtained.

Chemical constituents from Cordia alliodora and C. colloccoca (Boraginaceae) and their biological activities

Two new natural products, 5-O-[β-D-apiofuranosyl-(1→6)-β-d-glucopyranosyl]-1-isoindolinone (1) as well as N-(2E)-3-[(2S,3R)-2-(4-hydroxy-3-methoxyphenyl)-3-(hydroxymethyl)-7-methoxy-2,3-dihydro-1-benzofuran-5-yl]acryloylglycine (2), along with four known compounds (3-6), were isolated from the methanolic extract of Cordia alliodora root bark. Furthermore, the methanolic extract of Cordia colloccoca leaves, afforded the known flavonoids afzelin (7) and quercitrin (8). The isolated secondary metabolites were assayed for their antimicrobial activities against a panel of 6g positive and negative bacteria and three human pathogenic fungi. Moreover, their antiproliferative effect was also evaluated in vitro against the human non-small-cell bronchopulmonary carcinoma line NSCLC-N6, the epidermoid lung cancer cell line A549 as well as the normal human skin fibroblast cell line (AG01523).