Hongzhu Guo

Antidepressant-like effect of liquiritin from Glycyrrhiza uralensis in chronic variable stress induced depression model rats

Many flavonoids extracted from nature plants have been reported to exert antidepressant-like effect in animal studies. The present study was designed to observe the effects of liquiritin, a flavone compound derived from Glycyrrhiza uralensis, on the behaviors of chronic variable stress induced depression model rats and to explore the possible association between its antidepressant-like effect and antioxidative activity by measuring erythrocyte superoxide dismutase (SOD) activity and plasma malondialdehyde (MDA) level of the experimental animals. With the exposure to stressor once daily for consecutive 5 weeks, liquiritin and a positive control drug fluoxetine were administered via gastric intubation to rats once daily for consecutive 3 weeks from the 3rd week. The results showed that CVS reduced open-field activity and sucrose consumption significantly, but increased immobility time in forced swimming test. Treatment of liquiritin could effectively reverse alteration in immobility time and sucrose consumption but did not show significant effect on open-field activity. Moreover, liquiritin could increase SOD activity, inhibit lipid peroxidation, and lessen production of MDA, while fluoxetine did not. In conclusion, the present study demonstrated a potential antidepressant-like effect of liquiritin treatment on chronic variable stress induced depression model rats, which might be related to defense of liquiritin against oxidative stress.

Novel cytotoxic bufadienolides derived from bufalin by microbial hydroxylation and their structure–activity relationships

Microbial transformation was used to prepare novel cytotoxic bufadienolides. Twelve products (3-14) were obtained from bufalin (1) by the fungus Mucor spinosus. Their structures were elucidated by high-resolution mass spectroscopy (HR-MS) and extensive NMR techniques, including 1H NMR, 13C NMR, DEPT, 1H-1H correlation spectroscopy (COSY), two dimensional nuclear Overhauser effect correlation spectroscopy (NOESY), heteronuclear multiple quantum coherence (HMQC), and heteronuclear multiple bond coherence (HMBC). Compounds 3, 4, 9 and 11-14 are new mono- or dihydroxylated derivatives of bufalin with novel oxyfunctionalities at C-1beta, C-7beta, C-11beta, C-12beta and C-16alpha positions. The in vitro cytotoxic activities against human cancer cell lines of 3-14, together with 16 biotransformed products derived from cinobufagin (15-30) were determined by the MTT method, and their structure-activity relationships (SAR) were discussed.

Antidepressant-like effects of liquiritin and isoliquiritin from Glycyrrhiza uralensis in the forced swimming test and tail suspension test in mice

Two classic animal behavior despair tests--the Forced Swimming Test (FST) and the Tail Suspension Test (TST) were used to evaluate the antidepressant activity of liquiritin and isoliquiritin from Glycyrrhiza uralensis in mice. It was observed that both liquiritin and isoliquiritin at doses of 10, 20 and 40 mg/kg significantly reduced the immobility time in the FST and TST in mice 30 min after treatment. Measurement of locomotor activity indicated that liquiritin and isoliquiritin had no central nervous system (CNS)-stimulating effects. The main monoamine neurotransmitters and their metabolites in mouse brain regions were also simultaneously determined by HPLC-ECD. It was found that these two compounds significantly increased the concentrations of the main neurotransmitters 5-HT and NE in the hippocampus, hypothalamus and cortex. Liquiritin and isoliquiritin also significantly reduced the ratio of 5-HIAA/5-HT in the hippocampus, hypothalamus and cortex, slowing down 5-HT metabolism compared with mice treated with vehicle+stress. In conclusion, liquiritin and isoliquiritin produced significant antidepressant-like effects, and their mechanism of action may be due to increased 5-HT and NE in the mouse hippocampus, hypothalamus and cortex.

Specific 12β-Hydroxylation of Cinobufagin by Filamentous Fungi

ABSTRACT Biotransformation of natural products has great potential for producing new drugs and could provide in vitro models of mammalian metabolism. Microbial transformation of the cytotoxic steroid cinobufagin was investigated. Cinobufagin could be specifically hydroxylated at the 12β-position by the fungus Alternaria alternata. Six products from a scaled-up fermentation were obtained by silica gel column chromatography and reversed-phase liquid chromatography and were identified as 12β-hydroxyl cinobufagin, 12β-hydroxyl desacetylcinobufagin, 3-oxo-12β-hydroxyl cinobufagin, 3-oxo-12β-hydroxyl desacetylcinobufagin, 12-oxo-cinobufagin, and 3-oxo-12α-hydroxyl cinobufagin. The last five products are new compounds. 12β-Hydroxylation of cinobufagin by A. alternata is a fast catalytic reaction and was complete within 8 h of growth with the substrate. This reaction was followed by dehydrogenation of the 3-hydroxyl group and then deacetylation at C-16. Hydroxylation at C-12β also was the first step in the metabolism of cinobufagin by a variety of fungal strains. In vitro cytotoxicity assays suggest that 12β-hydroxyl cinobufagin and 3-oxo-12α-hydroxyl cinobufagin exhibit somewhat decreased but still significant cytotoxic activities. The 12β-hydroxylated bufadienolides produced by microbial transformation are difficult to obtain by chemical synthesis.

Microbial transformations of artemisinin by Cunninghamella echinulata and Aspergillus niger

Microbial transformations of artemisinin 1 by Cunninghamella echinulata (AS 3.3400) and Aspergillus niger (AS 3.795) were carried out. Two products, 10β-hydroxyartemisinin 2 and 3α-hydroxydeoxyartemisinin 3, were obtained. Their structures were identified on the basis of chemical and spectroscopic data. 10β-Hydroxyartemisinin is a new compound.

Biotransformation of cinobufagin by cell suspension cultures of Catharanthus roseus and Platycodon grandiflorum

Abstract The biotransformations of cinobufagin ( 1 ), an animal-originated bufadienolide, by cell suspension cultures of Catharanthus roseus and Platycodon grandiflorum were investigated. Incubation for 6 days of 1 with C. roseus yielded four products, desacetylcinobufotalin ( 2 ), 3-epi-desacetylcinobufagin ( 3 ), 1β-hydroxyl desacetylcinobufagin ( 4 ) and 3-epi-desacetylcinobufotalin ( 5 ), among which 4 is a new compound. Time course investigation revealed that the biotransformation rates of two major products, 2 and 3 , reached their highest levels of 44.7 and 16.5%, respectively, on the third day after substrate administration. Compounds 2 – 5 showed more potent cytotoxic activities against HL-60 cell lines than the parent compound 1 . A plausible biotransformation pathway is proposed to account for the formation of the observed products. From the culture supernatant of P. grandiflorum , 2 was isolated in 37.8% yield after 8 days of incubation with 1 . Cinobufotalin ( 6 ) and desacetylcinobufagin ( 7 ) were also obtained as minor products. The two plant suspension cultures exhibited similar transformation patterns on compound 1 .

Glucosylation of cinobufagin by cultured suspension cells of Catharanthus roseus

Abstract The biotransformation of cinobufagin by cell suspension cultures of Catharanthus roseus was investigated. After 6 days incubation, four new glucosylated derivatives, desacetylcinobufagin 16- O -β- d -glucoside, 3- epi -desacetylcinobufagin 16- O -β- d -glucoside, 3-oxo-desacetylcinobufagin 16- O -β- d -glucoside, and cinobufagin 3- O -β- d -glucoside, respectively, were isolated and identified on the basis of their physical and chemical data. This is the first report of bufadienolides with a glucosyl substituent at the C-16 position.

Biotransformation of triptolide by Cunninghamella blakesleana

Abstract Biotransformation of triptolide 1 by Cunninghamella blakesleana (AS 3.970) was carried out. Seven biotransformation products were obtained and four of them were characterized as new compounds. On the basis of their NMR and mass spectral data, their structures were characterized as 5α-hydroxytriptolide 2 , 1β-hydroxytriptolide 3 , triptodiolide 4 , 16-hydroxytriptolide 5 , triptolidenol 6 , 19α-hydroxytriptolide 7 and 19β-hydroxytriptolide 8 . All the new transformed products ( 2 , 3 , 7 and 8 ) were found to exhibit potent in vitro cytotoxicity against some human tumor cell lines.

Biotransformation of 20(S)-protopanaxadiol by Mucor spinosus

Biotransformation of 20(S)-protopanaxadiol (1) by the fungus Mucor spinosus AS 3.3450 yielded eight metabolites (2-9). On the basis of NMR and MS analyses, the metabolites were identified as 12-oxo-15alpha,27-dihydroxyl-20(S)-protopanaxadiol (2), 12-oxo-7beta,11alpha,28-trihydroxyl-20(S)-protopanaxadiol (3), 12-oxo-7beta,28-dihydroxyl-20(S)-protopanaxadiol (4), 12-oxo-15alpha,29-dihydroxyl-20(S)-protopanaxadiol (5), 12-oxo-7beta,15alpha-dihydroxyl-20(S)-protopanaxadiol (6), 12-oxo-7beta,11beta-dihydroxyl-20(S)-protopanaxadiol (7), 12-oxo-15alpha-hydroxyl-20(S)-protopanaxadiol (8), and 12-oxo-7beta-hydroxyl-20(S)-protopanaxadiol (9), respectively. Among them, 2-5, 7, and 8 are new compounds. These results indicated that M. spinosus could catalyze the specific C-12 dehydrogenation of 20(S)-protopanaxadiol, as well hydroxylation at different positions. These biocatalytic reactions may be difficult for chemical synthesis. The biotransformed products showed weak in vitro cytotoxic activities.

Mechanisms of pseudolaric acid B-induced apoptosis in Bel-7402 cell lines.

Previous studies have shown that pseudolaric acid B (PB) would cause apoptosis in human tumor cell lines. However, the mechanisms of PB induced apoptosis are still unclear. In the present study, the mechanisms of PB induced apoptosis in the human hepatocellular carcinoma Bel-7402 cell line were investigated by measuring cell viability, rate of apoptosis, cell cycle, detecting DNA fragmentation, and measuring caspase-3 activation. The results indicated that PB inhibited Bel-7402 cell viability and induced cell death by causing DNA fragmentation, up regulating the early and late apoptotic rates, activating caspase-3 protein, and detaining the cell cycle in the G2/M phases. Additionally, PB-induced apoptosis was a dose- and time-dependent manner. These observations suggest that PB-induced apoptosis occurs through a caspase-dependent pathway and detains the cell cycle in the G2/M phase.