Inhibition of nonenzymic lipid peroxidation by benzylisoquinoline alkaloids

An Overview of Chemistry, Kinetics, Toxicity and Therapeutic Potential of Boldine in Neurological Disorders

Boldine is an alkaloid obtained from the medicinal herb Peumus boldus (Mol.) (Chilean boldo tree; boldo) and belongs to the family Monimiaceae. It exhibits a wide range of pharmacological effects such as antioxidant, anticancer, hepatoprotective, neuroprotective, and anti-diabetic properties. There is a dearth of information regarding its pharmacokinetics and toxicity in addition to its potential pharmacological activity. Boldine belongs to the aporphine alkaloid class and possesses lipophilic properties which enable its efficient absorption and distribution throughout the body, including the central nervous system. It exhibits potent free radical scavenging activity, thereby reducing oxidative stress and preventing neuronal damage. Through a variety of neuroprotective mechanisms, including suppression of AChE and BuChE activity, blocking of connexin-43 hemichannels, pannexin 1 channel, reduction of NF-κβ mediated interleukin release, and glutamate excitotoxicity which successfully reduces neuronal damage. These results point to its probable application in reducing neuroinflammation and oxidative stress in epilepsy, Alzheimer's disease (AD), and Parkinson's disease (PD). Moreover, its effects on serotonergic, dopaminergic, opioid, and cholinergic receptors were further investigated in order to determine its applicability for neurobehavioral dysfunctions. The article investigates the pharmacokinetics of boldine and reveals that it has a low oral bioavailability and a short half-life, requiring regular dosage to maintain therapeutic levels. The review studies boldine's potential therapeutic uses and mode of action while summarizing its neuroprotective benefits.  Given the favorable results for boldine as a potential neurotherapeutic drug in laboratory animals, more research is required. However, in order to optimise its therapeutic potential, it must be more bioavailable with fewer detrimental side effects.

Structure–antioxidant activity relationships in boldine and glaucine: a DFT study

DFT calculations indicate that boldine and glaucine exhibit direct antioxidant activity through the HAT and SPLET (at high pH values) mechanisms.

Antiplasmodial activity and cytotoxicity, isolation of active alkaloids, and dereplication of Xylopia sericea leaves ethanol extract by UPLC-DAD-ESI-MS/MS

Objectives

To assess the antiplasmodial activity of the ethanol extract of Xylopia sericea leaves, Annonaceae, often associated with antimalarial use and to perform a bioguided isolation of active compounds.

Methods

Dereplication of ethanol extract by the UPLC-DAD-ESI-MS/MS technique allowed the identification of the major constituents, isolation and identification of alkaloids. The antiplasmodial and cytotoxic activity of the extract, fractions and isolated compounds was evaluated against the chloroquine-resistant W2 strain Plasmodium falciparum and HepG2 cells, respectively.

Key findings

Ethanol extract showed high reduction of parasitemia as well as moderate cytotoxicity (86.5 ± 3.0% growth inhibition at 50 μg/ml and CC50 72.1 ± 5.1 μg/ml, respectively). A total of eight flavonoids were identified, and two aporphine alkaloids, anonaine and O-methylmoschatoline, were isolated. Anonaine disclosed significant antiplasmodial effect and moderate cytotoxicity (IC50 23.2 ± 2.7 μg/ml, CC50 38.3 ± 2.3 μg/ml, SI 1.6) while O-methylmoschatoline was not active against P. falciparum and showed a low cytotoxicity (33.5 ± 1.9% growth inhibition at 50 μg/ml, CC50 274.4 ± 0.5 μg/ml).

Conclusions

Characterization of Xylopia sericea leaves ethanol extract by UPLC-DAD-ESI-MS/MS as well as its antiplasmodial activity and the occurrence of anonaine and O-methylmoschatoline in this Xylopia species are reported by the first time.

Ethnobotany, phytochemistry and pharmacology of Stephania rotunda Lour

ETHNOPHARMACOLOGICAL RELEVANCE

Stephania rotunda Lour. (Menispermaceae) is an important traditional medicinal plant that is grown in Southeast Asia. The stems, leaves, and tubers have been used in the Cambodian, Lao, Indian and Vietnamese folk medicine systems for years to treat a wide range of ailments, including asthma, headache, fever, and diarrhoea.

AIM OF THE REVIEW

To provide an up-to-date, comprehensive overview and analysis of the ethnobotany, phytochemistry, and pharmacology of Stephania rotunda for its potential benefits in human health, as well as to assess the scientific evidence of traditional use and provide a basis for future research directions.

MATERIAL AND METHODS

Peer-reviewed articles on Stephania rotunda were acquired via an electronic search of the major scientific databases (Pubmed, Google Scholar, and ScienceDirect). Data were collected from scientific journals, theses, and books.

RESULTS

The traditional uses of Stephania rotunda were recorded in countries throughout Southeast Asia (Cambodia, Vietnam, Laos, and India). Different parts of Stephania rotunda were used in traditional medicine to treat about twenty health disorders. Phytochemical analyses identified forty alkaloids. The roots primarily contain l-tetrahydropalmatine (l-THP), whereas the tubers contain cepharanthine and xylopinine. Furthermore, the chemical composition differs from one region to another and according to the harvest period. The alkaloids exhibited approximately ten different pharmacological activities. The main pharmacological activities of Stephania rotunda alkaloids are antiplasmodial, anticancer, and immunomodulatory effects. Sinomenine, cepharanthine, and l-stepholidine are the most promising components and have been tested in humans. The pharmacokinetic parameters have been studied for seven compounds, including the three most promising compounds. The toxicity has been evaluated for liriodenine, roemerine, cycleanine, l-tetrahydropalmatine, and oxostephanine.

CONCLUSION

Stephania rotunda is traditionally used for the treatment of a wide range of ailments. Pharmacological investigations have validated different uses of Stephania rotunda in folk medicine. The present review highlights the three most promising compounds of Stephania rotunda, which could constitute potential leads in various medicinal fields, including malaria and cancer.

The pharmacological activities of (-)-anonaine

Several species of Magnoliaceae and Annonaceae are used in Traditional Chinese Medicine. (−)-Anonaine, isolated from several species of Magnoliaceae and Annonaceae, presents antiplasmodial, antibacterial, antifungal, antioxidation, anticancer, antidepression, and vasorelaxant activity. This article provides an overview of the pharmacological functions of (−)-anonaine.

Annonaceae: bio-resource for tomorrow's drug discovery

One of the rich sources of lead compounds is the Angiosperms. Many of these lead compounds are useful medicines naturally, whereas others have been used as the basis for synthetic agents. These are potent and effective compounds, which have been obtained from plants, including anti-cancer (cytotoxic) agents, anti-malaria (anti-protozoal) agents, and anti-bacterial agents. Today, the number of plant families that have been extensively studied is relatively very few and the vast majorities have not been studied at all. The Annonaceae is the largest family in the order Magnoliales. It includes tropical trees, bushes, and climbers, which are often used as traditional remedies in Southeast Asia. Members of the Annonaceae have the particularity to elaborate a broad spectrum of natural products that have displayed anti-bacterial, anti-fungal, and anti-protozoal effects and have been used for the treatment of medical conditions, such as skin diseases, intestinal worms, inflammation of the eyes, HIV, and cancer. These special effects and the vast range of variation in potent compounds make the Annonaceae unique from other similar families in the Magnoliales and the Angiosperms in general. This paper attempts to summarize some important information and discusses a series of hypotheses about the effects of Annonaceae compounds.

(-)-Anonaine induces DNA damage and inhibits growth and migration of human lung carcinoma h1299 cells

The anticancer effects of (-)-anonaine were investigated in this current study. (-)-Anonaine at concentration ranges of 50-200 μM exhibited significant inhibition to cell growth and migration activities on human lung cancer H1299 cells at 24 h, albeit cell cycle analyses showed that (-)-anonaine at the above concentration ranges did not cause any significant changes in cell-cycle distributions. Significant nuclear damages of H1299 cells were observed with 10-200 μM (-)-anonaine treatment in a comet assay, whereas higher concentrations (6 and 30 mM) of (-)-anonaine concentrations were required to cause DNA damages in an in vitro plasmid cleavage assay. In summary, our results demonstrated that (-)-anonaine exhibited dose-dependent antiproliferatory, antimigratory, and DNA-damaging effects on H1299 cells. We inferred that (-)-anonaine can cause cell-cycle arrest and DNA damage to hamper the physiological behavior of cancer cells at 72 h, and therefore, it can be useful as one of the potential herbal supplements for chemoprevention of human lung cancer.

Cinnamoyl- and hydroxycinnamoyl amides of glaucine and their antioxidative and antiviral activities

The aporphine alkaloid glaucine has been converted into 3-aminomethylglaucine and its free amino group has been linked to cinnamic, ferulic, sinapic, o-, and p-coumaric acids. The antioxidative potential of the synthesized amides was studied against DPPH(*) test. All of the tested compounds demonstrated higher radical scavenging activity than glaucine and 3-aminomethylglaucine, and lower antioxidative effect than the free hydroxycinnamic acids. The newly synthesized compounds were tested in vitro for antiviral activity against viruses belonging to different taxonomic groups.

(-)-Anonaine induces apoptosis through Bax- and caspase-dependent pathways in human cervical cancer (HeLa) cells

(-)-Anonaine has been shown to have some anticancer activities, but the mechanisms of (-)-anonaine inducing cell death of human cancer cells is not fully understood. We investigated the mechanisms of apoptosis induced by (-)-anonaine in human HeLa cancer cells. Treatment with (-)-anonaine induces dose-dependent DNA damage that is correlated with increased intracellular nitric oxide, reactive oxygen species, glutathione depletion, disruptive mitochondrial transmembrane potential, activation of caspase 3, 7, 8, and 9, and poly ADP ribose polymerase cleavage. Our data indicate that (-)-anonaine up-regulated the expression of Bax and p53 proteins in HeLa cancer cells. The apoptosis and expression of Bax induced by (-)-anonaine could be inhibited when the HeLa cells were pretreated with Boc-Asp(OMe)-fmk, which is a broad caspases inhibitor. There was no obvious DNA damage in the (-)-anonaine-treated Madin-Darby canine kidney and Vero cell lines. Both Madin-Darby canine kidney and Vero cell lines are kidney epithelial cellular morphology. These results suggest that (-)-anonaine might be considered a potent compound for chemotherapy against cervical cancer or a health food supplement for cancer chemoprevention.

Effects of anonaine on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells

The effects of anonaine, an aporphine isoquinoline alkaloid, on dopamine biosynthesis and L-DOPA-induced cytotoxicity in PC12 cells were investigated. Anonaine at concentration ranges of 0.01-0.2 microM showed a significant inhibition of dopamine content at 24 h, with an IC(50) value of 0.05 microM. Anonaine at 0.05 microM inhibited tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) activities to 38.4-40.2% and 78.4-90.2% of control levels at 12-24 h and 3-6 h, respectively. TH activity was more influenced than AADC activity. Anonaine also decreased intracellular cyclic AMP levels, but not intracellular Ca(2+) concentrations. In addition, anonaine (0.05 microM) reduced L-DOPA (50 microM and 100 microM)-induced increases in dopamine content at 24 h. However, anonaine (0.05 microM) did not enhance L-DOPA (50 microM and 100 microM)-induced cell death after 24 h. These results suggest that anonaine inhibits dopamine biosynthesis by mainly reducing TH activity without aggravating L-DOPA-induced cytotoxicity in PC12 cells.

Liriodenine inhibits dopamine biosynthesis and L-DOPA-induced dopamine content in PC12 cells

The inhibitory effects of liriodenine, an aporphine isoquinoline alkaloid, on dopamine biosynthesis and L-DOPA-induced dopamine content increases in PC12 cells were investigated. Treatment of PC12 cells with 5-10 microM liriodenine significantly decreased the intracellular dopamine content in a concentration-dependent manner (IC50 value, 8.4 microM). Liriodenine was not cytotoxic toward PC12 cells at concentrations up to 20 microM. Tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC) activities were inhibited by 10 microM liriodenine to 20-70% and 10-14% of control levels at 3-12 h, respectively; TH activity was more influenced than AADC activity. The levels of TH mRNA, intracellular cyclic AMP and basal Ca2+ concentration were also decreased by 10 microM liriodenine. In addition, 10 microM liriodenine reduced L-DOPA (20-100 microM)-induced increases in dopamine content. However, 10 microM liriodenine resulted in a protective effect against L-DOPA (50-100 microM)-induced cytotoxicity. These results suggest that liriodenine regulates dopamine biosynthesis by partially reducing TH activity and TH gene expression and has protective effects against L-DOPA-induced cytotoxicity in PC12 cells.

Antinociceptive and free radical scavenging activities of alkaloids isolated from Lindera angustifolia Chen

Lindera angustifolia Chen is a folk medicine used for the treatment of contusions-induced swelling, rheumatic pains and bellyache in south and the middle part of China. Phytochemical studies showed that aporphine and benzyltetrahydroisoquinoline alkaloids are the characteristic constituents of this plant. In this study, we evaluated the antinociceptive and free radical scavenging properties of six aporphine and two benzyltetrahydroisoquinoline alkaloids isolated from the root of Lindera angustifolia. All alkaloids except magnocurarine exhibited remarkable radical scavenging effects (36-90% scavenging at 25-100microg/ml) in DPPH radical scavenging test, among them norisocorydine showed the hightest activity (SC(50): 14.1microg/ml). Antinociceptive activities were tested by using acetic acid-induced writhing and formalin test at dose of 20mg/kg. Norisocorydine exhibited the highest antinociceptive ability with 83.5% writhing inhibition. Boldine, norboldine showed significant antinociceptive activity with 76.3% and 74.6% writhing inhibition respectively. Indomethacin was used as positive control, which showed 67.8% writhing inhibition at dose of 10mg/kg. Most of the compounds, except N-ethoxycarbonyllaurotetanine and magnocurarine, could significantly inhibit the phase I reaction (P<0.01), and all of them inhibited the phase II reaction (P<0.001) in the formalin tests (indomethacin and morphine were used as positive drugs). The antinociceptive effects exhibited a structure-activity relationship similar to that of the free radical scavenging activities. Above results suggested that the alkaloids from the root of Lindera angustifolia possess both free radical scavenging and antinociceptive activities, and the antinociceptive activity seems to be related to the free radical scavenging effect.

Boldine and its antioxidant or health-promoting properties

The increasing recognition of the participation of free radical-mediated oxidative events in the initiation and/or progression of cardiovascular, tumoural, inflammatory and neurodegenerative disorders, has given rise to the search for new antioxidant molecules. An important source of such molecules has been plants for which there is an ethno-cultural base for health promotion. An important example of this is boldo (Peumus boldus Mol.), a chilean tree whose leaves have been traditionally employed in folk medicine and is now widely recognized as a herbal remedy by a number of pharmacopoeias. Boldo leaves are rich in several aporphine-like alkaloids, of which boldine is the most abundant one. Research conducted during the early 1990s led to the discovery that boldine is one of the most potent natural antioxidants. Prompted by the latter, a large and increasing number of studies emerged, which have focused on characterizing some of the pharmacological properties that may arise from the free radical-scavenging properties of boldine. The present review attempts to exhaustively cover and discuss such studies, placing particular attention on research conducted during the last decade. Mechanistic aspects and structure-activity data are discussed. The review encompasses pharmacological actions, which arise from its antioxidant properties (e.g., cyto-protective, anti-tumour promoting, anti-inflammatory, anti-diabetic and anti-atherogenic actions), as well as those that do not seem to be associated with such activity (e.g., vasorelaxing, anti-trypanocidal, immuno- and neuro-modulator, cholagogic and/or choleretic actions). Based on the pharmacological and toxicological data now available, further research needs and recommendations are suggested to define the actual potential of boldine for its use in humans.

Antiradical and antioxidant activities of alkaloids isolated from Mahonia aquifolium. Structural aspects

The antioxidant activities of three alkaloids isolated from Mahonia aquifolium--berberine, jatrorrhizine, and magnoflorine--were studied with respect to their structural aspects, particularly the presence and the position of -OH groups, steric conditions of unpaired electron delocalization and parameters of lipophilicity and hydration energy. The antiradical activities of the compounds tested were evaluated as the reactivities toward free stable alpha,alpha'-diphenyl-beta-picrylhydrazyl radical (DPPH). The antioxidant features of the alkaloids tested were investigated in heterogeneous membrane system of DOPC liposomes stressed by peroxidative damage induced by AAPH azoinitiator. Both alkaloids bearing free phenolic groups--jatrorrhizine and magnoflorine--showed better activities in both systems used than berberine not bearing any readily abstractable hydrogen on its skeleton. The former two showed antiperoxidative efficiency in DOPC liposomal membrane comparable to that of an effective scavenger of peroxyl radicals--stobadine-and higher than that of Trolox. We conclude that the favorable antioxidant features of the hydroxylated alkaloids are most probably ensured by the combination of reasonably high antiradical reactivity with high lipophilicity, however, the solvation process was found to markedly interfere with these beneficial effects.

Photostability and photoprotection factor of boldine and glaucine

Boldine hydrochloride was more photounstable than boldine after irradiation with UVB (lambda = 300 nm). However, photoconsumption quantum yields, for glaucine hydrochloride (6.5 x 10(-2)) and boldine hydrochloride (6.7 x 10(-2)) in air, were quite similar. The photolysis was oxygen dependent in both cases, and the effect over the kinetics after the addition of 2,2,6,6-tetramethyl-1-piperidinyloxy suggested free radicals participation. The fact that the antioxidative capacity of boldine and boldine hydrochloride did not change during the photolysis, suggests that the phenolic structure remains unchanged in the photoproducts, corroborated with the photoproducts analysis. The photoprotection capacity was evaluated before and after irradiation. Results indicate that the values before irradiation are similar for all three compounds, only glaucine increasing its capacity with length of irradiation time.

Coptidis Rhizoma: protective effects against peroxynitrite-induced oxidative damage and elucidation of its active components

We have investigated the protective effects of Coptidis Rhizoma against peroxynitrite (ONOO(-))-induced oxidative damage and have elucidated the active components of this preparation. In an in-vitro system, Coptidis Rhizoma extract scavenged ONOO(-) and its precursors, nitric oxide (NO) and superoxide anion (O(2)(-)). This scavenging activity was more marked for ONOO(-) than its precursors. In addition, against 3-morpholinosydnonimine-induced cellular damage, this extract significantly reduced cellular ONOO(-) formation and increased cell viability. In an in-vivo lipopolysaccharide plus ischaemia-reperfusion system that generated ONOO(-), the administration of Coptidis Rhizoma extract at 50 and 100 mg kg(-1)/day for 30 days exerted greater inhibition of ONOO(-) than NO and O(2)(-). This suggested that it acted as a direct scavenger of ONOO(-) rather than as a scavenger of its precursors. Moreover, the suppression of the activities of the antioxidative enzymes superoxide dismutase, catalase and glutathione peroxidase was significantly attenuated by the administration of Coptidis Rhizoma extract. Furthermore, the extract ameliorated renal dysfunction judged by decreasing serum urea nitrogen and creatinine levels. To elucidate the active components of Coptidis Rhizoma extract, we evaluated and compared the effects of the phenol plus alkaloid and alkaloid fractions on ONOO-induced damage. We found that the alkaloid fraction consisting of berberine, palmatine and coptisine was the most effective at protecting against ONOO(-). We confirmed that berberine (10 and 20 mg kg(-1)/day for 10 days), the main and most active alkaloid in Coptidis Rhizoma extract, was also protective, exerting NO-, O(2)(-)- and ONOO(-)-scavenging activities. This study suggested that Coptidis Rhizoma could protect against ONOO(-)-induced oxidative damage and that this effect was mainly attributable to the constituent alkaloids, especially berberine. This study is the first to demonstrate an antioxidative effect of alkaloids, including berberine, against ONOO(-)-induced damage.

Biological disposition of boldine: in vitro and in vivo studies

Boldine is a natural compound with well-established free radical scavenger and hepatoprotective properties. The further exploration of its actual therapeutic potential as an antioxidant is, however, partially limited by the absence of knowledge on its pharmacokinetics. In the present studies, we provide information on the in vitro and in vivo biological disposition of boldine. The addition of 200 microM boldine to an isolated rat hepatocyte suspension was followed by a time-dependent (0-60 min) disappearance of boldine from the extracellular medium. This decline was associated with an early (first 2 min) and swift accumulation (1600 microM) of boldine within the cells. Although the intracellular concentration of boldine diminished, boldine was always found to occur within the cells at concentrations substantially higher than those initially added to the preparation. Boldine was also concentration-dependently removed from the extracellular medium by isolated rat livers portally perfused with the antioxidant. In vivo studies, conducted in rats, revealed that following either its oral or its intravenous administration, plasma boldine concentrations declined rapidly and according to an apparently first order type of kinetics. After its oral administration (50 or 75 mg/kg), boldine was rapidly (within 30 min) absorbed and preferentially concentrated in the liver, with substantially lower concentrations being found in the brain and heart. Maximal hepatic concentrations of boldine were found to be equal to or greater than those needed to afford antioxidant and hepatoprotective effects in vitro.

Potent antiperoxidation activity of the bisbenzylisoquinoline alkaloid cepharanthine: the amine moiety is responsible for its pH-dependent radical scavenge activity

The bisbenzylisoquinoline alkaloid cepharanthine, which has been considered to exhibit antiperoxidation activity due to its membrane stabilizing effect, was found to scavenge radicals such as .OH and DPPH (1,1-diphenyl-2-picrylhydrazyl) in solution, and to inhibit lipid peroxidation in mitochondria and liposomes by Fe2+/ADP. The antiperoxidation activity of cepharanthine in rat liver mitochondria initiated by Fe2+/ADP at pH 7.4 was much greater than that of alpha-tocopherol, its half-inhibitory concentration being about 23 microM. However, cepharanthine was effective only at neutral pH values such as pH 7.4, not in a moderately acidic pH region below pH 6.5. Accordingly, the neutral form of the deprotonated amine moiety in the tetrahydroisoquinoline ring is concluded to be responsible for the radical scavenging activity of cepharanthine. There are two amine moieties in the cepharanthine molecule, but we specified the effective amine moiety from the antiperoxidation activities of the imine analogs of cepharanthine.

Inhibitory effects of bulbocapnine on dopamine biosynthesis in PC12 cells

The effects of bulbocapnine, an aporphine isoquinoline alkaloid, on dopamine biosynthesis in PC12 cells were investigated. Bulbocapnine showed 45.2% inhibition on dopamine content in PC12 cells at a concentration of 20 microM for 12 h. The IC50 value of bulbocapnine was 26.7 microM. Bulbocapnine at concentrations up to 80 microM was not cytotoxic towards PC12 cells. Tyrosine hydroxylase (TH) activity was inhibited by the treatment of bulbocapnine in PC12 cells (24.4% inhibition at 20 microM). Bulbocapnine at 20 microM also decreased the intracellular Ca2+ concentration by 12.9% inhibition relative to control in PC12 cells. However, TH mRNA level was not altered by bulbocapnine treatment. These results suggest that the inhibition of TH activity by bulbocapnine might be involved in at least one component of the reduction of dopamine biosynthesis in PC12 cells.

Structure-antioxidative activity relationships in benzylisoquinoline alkaloids

The antioxidative properties of the aporphines boldine, glaucine and apomorphine, and of the benzyltetrahydroisoquinolines (+/-)-coclaurine and (+/-)-norarmepavine were compared in the brain homogenate autoxidation model. The IC50 values found lay in the 16-20 microM range for the aporphines and were 131.7 microM, and 79.3 microM for coclaurine and norarmepavine, respectively. These results indicate that the antioxidative capacity (AC) of these compounds is related to the presence of the biphenyl system rather than phenol groups. The non-phenolic glaucine inhibited the 2,2'-azobis-(2-amidinopropane)(AAP)-induced inactivation of lysozyme with an IC50 value of 12 microM, while the corresponding values for the phenolic coclaurine and norarmepavine were 10 and 20 microM, respectively. N-Methylation of glaucine to its quaternary ammonium reduced its protective effect by two-thirds. This result suggests that a benzylic hydrogen neighbouring a nitrogen lone electron pair may be the key to the protective effect of non-phenolic aporphines.

Trypanocidal effect of boldine and related alkaloids upon several strains of Trypanosoma cruzi

The alkaloids boldine, glaucine, predicentrine, apomorphine, coclaurine, norarmepavine and codeine were tested against the epimastigotes of the Tulahuén and LQ strains and the DM 28c clone of Trypanosoma cruzi. The micromolar concentration to inhibit 50% of the culture growth (Tulahuén strain) for apomorphine, glaucine, predicentrine, boldine, norarmepavine, coclaurine and codeine were 29, 90, 85, 110, 310, 580 and > 1000 respectively. Similar values were obtained with the LQ strain and the DM 28c clone. The most active compounds in inhibiting culture growth also inhibited cell respiration, suggesting that these drugs may act by blocking mitochondrial electron transport. The trypanocidal effects of these alkaloids appear to be correlated with their antioxidative activities.

Boldo and boldine: an emerging case of natural drug development

Boldo (Peumus boldus Mol.), a Chilean tree traditionally employed in folk medicine and recognized as a herbal remedy in a number of pharmacopoeias, mainly for the treatment of liver ailments, has recently been the subject of increasing attention. Boldine, in particular, the major and most characteristic alkaloidal constituent of this plant species, now emerges as its most interesting active principle from the pharmacological viewpoint. The recent demonstration that boldine is an effective antioxidant in both biological and non-biological systems has opened up the perspective of a broad range of uses in medicine and industry. Given the toxicological data on this alkaloid, its antioxidative properties situate it as a potentially useful substance in many disease states featuring free-radical related oxidative injury. This review attempts to cover and discuss the studies conducted over the last four decades on the chemical and pharmacological properties of boldo and its main constituent.

Iron-reducing and free-radical-scavenging properties of apomorphine and some related benzylisoquinolines

The scavenging and iron-reducing properties of a series of benzylisoquinolines of natural and synthetic origin have been studied. Bulbocapnine, boldine, glaucine, and stepholidine acted as scavengers of hydroxyl radical in the deoxyribose degradation by Fe(3+)-EDTA + H2O2. On the contrary, laudanosoline, apomorphine, protopapaverine, anonaine, and tetrahydroberberine increased deoxyribose degradation by a mechanism related to generation of superoxide anion. Only apomorphine had a stimulating effect in the system using citrate instead of ethylenediaminetetraacetic acid (EDTA) as well as in the absence of chelator. Apomorphine also stimulated DNA damage by Cu2+. The iron-ion reducing ability of apomorphine and laudanosoline was confirmed using cytochrome c. Both compounds scavenged peroxyl radicals in an aqueous medium, while in Fe(3+)-induced microsomal lipid peroxidation apomorphine acted as an inhibitor and laudanosoline stimulated the process. It is suggested that in microsomes the chain-breaking antioxidant properties of apomorphine overcome its possible influence on redox cycling of iron, or prooxidant properties.

Antioxidant action of benzylisoquinoline alkaloids

The antioxidant action of a series of benzylisoquinoline alkaloids has been investigated. Laudanosoline, protopapaverine, anonaine, apomorphine, glaucine, boldine, bulbocapnine, tetrahydroberberine and stepholidine produced a dose-dependent inhibition of microsomal lipid peroxidation induced by Fe2+/ascorbate, CCl4/NADPH or by Fe3+ ADP/NADPH. Apomorphine exerted the highest inhibitory effects in the three systems of induction used, with a potency higher than propyl gallate. Laudanosoline was particularly effective in the first system, while bulbocapnine and anonaine were more potent when CCl4/NADPH or Fe3(+)-ADP/NADPH were used as inducers. Laudanosoline, protopapaverine, apomorphine, tetrahydroberberine and stepholidine were also potent inhibitors of nitroblue tetrazolium (NBT) reduction. The presence of a free hydroxyl group or preferably of a catechol group is a feature relevant for inhibition of lipid peroxidation and NBT reduction, nevertheless the antioxidant activity of benzylisoquinoline alkaloids cannot be only ascribed to the formation of phenoxy radicals and other free radical species may be formed during aporphine and tetrahydroprotoberberine oxidation. The influence of this series of compounds on the time course of lipid peroxidation suggests that some of them, like apomorphine and boldine act as chain-breaking antioxidants.