Six flavonoids, persicogenin (1), artemetin (2), luteolin (3), penduletin (4), vitexicarpin (5) and chrysosplenol-D (6), have been isolated for the first time as new cell cycle inhibitors from Vitex trifolia L., a Chinese folk medicine used to treat cancers, through a bioassay-guided separation procedure. They were identified by spectroscopic methods. The inhibitory effects of 1–6 on the proliferation of mammalian cancer cells have been evaluated by the SRB (sulforhodamine B) method and their effects on cell cycle and apoptosis investigated by flow cytometry with the morphological observation under light microscope and by agarose-gel electrophoresis to detect internucleosomal DNA fragmentation. Compounds 1–6 inhibited the proliferation of mouse tsFT210 cancer cells with the IC₅₀s (μg ml⁻¹) > 100 (inhibition rate at 100 μg ml⁻¹, 47.9%) for 1, >100 (inhibition rate at 100 μg ml⁻¹, 49.6 %) for 2, 10.7 for 3, 19.8 for 4, 0.3 for 5, and 3.5 for 6. Flow cytometric investigations for 1–6 demonstrated that 1–5 mainly inhibited cell cycle at the G₂/M phase in a dose-dependent manner with a weak induction of apoptosis on the tsFT210 cells, while 6 induced mainly apoptosis of the same tsFT210 cells also in a dose-dependent manner together with a weak inhibition of the cell cycle at the G₀/G₁ and G₂/M phases, demonstrating that 1–6 exert their anti-proliferative effect on tsFT210 cells through inhibiting cell cycle and inducing apoptosis. In contrast to the cell cycle G₂/M phase inhibitory main effect on tsFT210 cells, 5 induced mainly apoptosis on human myeloid leukemia K562 cells with a weak inhibition of the cell cycle at the G₂/M phase. The present result provides flavonoids 1–6 as new cell cycle inhibitors and 1 and 4 as new anticancer flavonoids, which not only provide the first example of cell cycle G₂/M phase inhibitory and apoptosis-inducing constituents of V. trifolia L. but also explain the use of Vitex trifolia L. by Chinese people to treat cancers.

A new approach to activate silent gene clusters for dormant secondary metabolite production has been developed by introducing gentamicin-resistance to an originally inactive, marine-derived fungal strain Penicillium purpurogenum G59. Upon treatment of the G59 spores with a high concentration of gentamicin in aqueous DMSO, a total of 181 mutants were obtained by single colony isolation. In contrast to the strain G59, the EtOAc extracts of nine mutant cultures showed inhibitory effects on K562 cells, indicating that the nine mutants had acquired capability to produce antitumor metabolites. This was evidenced by TLC and HPLC analysis of EtOAc extracts of G59 and the nine mutants. Further isolation and characterization demonstrated that four antitumor secondary metabolites, janthinone (1), fructigenine A (2), aspterric acid methyl ester (3) and citrinin (4), were newly produced by mutant 5-1-4 compared to the parent strain G59, and which were also not found in the secondary metabolites of other Penicillium purpurogenum strains. However, Compounds 1–4 inhibited the proliferation of K562 cells with inhibition rates of 34.6% (1), 60.8% (2), 31.7% (3) and 67.1% (4) at 100 μg/mL, respectively. The present study demonstrated the effectiveness of a simple, yet practical approach to activate the production of dormant fungal secondary metabolites by introducing acquired resistance to aminoglycoside antibiotics, which could be applied to the studies for eliciting dormant metabolic potential of fungi to obtain cryptic secondary metabolites.

Two new drimenyl cyclohexenone derivatives, named purpurogemutantin (1) and purpurogemutantidin (2), and the known macrophorin A (3) were isolated from a bioactive mutant BD-1-6 obtained by random diethyl sulfate (DES) mutagenesis of a marine-derived Penicillium purpurogenum G59. Structures and absolute configurations of 1 and 2 were determined by extensive spectroscopic methods, especially 2D NMR and electronic circular dichroism (ECD) analysis. Possible biosynthetic pathways for 1–3 were also proposed and discussed. Compounds 1 and 2 significantly inhibited human cancer K562, HL-60, HeLa, BGC-823 and MCF-7 cells, and compound 3 also inhibited the K562 and HL-60 cells. Both bioassay and chemical analysis (HPLC, LC-ESIMS) demonstrated that the parent strain G59 did not produce 1–3, and that DES-induced mutation(s) in the mutant BD-1-6 activated some silent biosynthetic pathways in the parent strain G59, including one set for 1–3 production.

Carbazole alkaloids, 3-methylcarbazole (1), murrayafoline A (2), girinimbine (3), mahanimbine (4) and bicyclomahanimbine (5), were isolated for the first time from Clausena dunniana Levl. by bioassay-guided separation procedure and were identified by spectroscopic methods. Compounds 1 - 5 showed growth inhibitory activity (1, IC₅₀ 25 w g/ml) on human fibrosarcoma HT-1080 cells and cell cycle M-phase inhibitory (2, MIC 0.78 w g/ml) and apoptosis inducing (2, MIC 1.56 w g/ml; 3, MIC 25 w g/ml; 4, MIC 20 w g/ml; 5, MIC 30 w g/ml) activities on mouse tsFT210 cells, respectively, and 2 - 5 provided the first examples of carbazole alkaloids as new cell cycle inhibitors and apoptosis inducers.

A new polyoxygenated sterol, sterolic acid (1), three new breviane spiroditerpenoids, breviones I–K (2–4), and the known breviones (5–8), were isolated from the crude extract of a Penicillium sp. obtained from a deep sea sediment sample that was collected at a depth of 5115 m. The structures of 1–4 were elucidated primarily by NMR experiments, and 1 was further confirmed by X-ray crystallography. The absolute configurations of 2 and 3 were deduced by comparison of their CD spectra with those of the model compounds. Compounds 2 and 5 showed significant cytotoxicity against MCF-7 cells, which is comparable to the positive control cisplatin.

Three new (1–3) and 11 known (4–14) C25 steroids with an unusual bicyclo[4.4.1]A/B ring system were isolated by tracing newly produced metabolites in the EtOAc extract of an antitumor mutant AD-1-2 obtained by the diethyl sulphate (DES) mutagenesis of a marine-derived Penicillium purpurogenum G59. HPLC-PDAD-UV and HPLC-ESI-MS analyses indicated that the G59 strain did not produce these metabolites and the production of 1–14 in the mutant AD-1-2 extract was caused by the activation of silent metabolites in the original G59 strain by DES mutagenesis. The structures of the new compounds, named antineocyclocitrinols A (1) and B (2) and 23-O-methylantineocyclocitrinol (3), including their absolute configurations were determined by various spectroscopic methods, especially the NMR and Mo₂-induced CD analyses. Compounds 1–3 provide the first examples of the C25 bicyclo[4.4.1]A/B ring steroids with the Z-configuration of 20,22-double bond. All of 1–14 weakly inhibited several human cancer cell lines to varying extents. These results provided additional examples for the successful application of the chemical mutagenesis strategy using DES to discover new compounds by activating silent metabolites in fungal isolates and supported also the effectiveness and usefulness of this new strategy.