Theoretical Bases of Optimization of the Modes of Postharvest Treatment of Alkaloid-Synthesizing Medicinal Plants

The method of disks in combination with thin-layer chromatography and spectrophotometry was used for a comparative evaluation of the efficiency of different methods of fixing and fermentation of medicinal plants (leaves). Medicinal plant species capable of synthesizing alkaloids of various structural types (isoquinoline derivatives including benzophenanthridines, bisbenzylisoquinoline, quaternary protoberberines, and aporphines, as well as steroid and diterpene alkaloids) were used. The methods of fixing and fermentation were shown to exert a substantial effect on both the qualitative and quantitative composition of alkaloids. This difference in the alkaloid composition was found to represent the superposition of three independent and, to a large extent, opposite processes: catabolism of alkaloids, interaction of alkaloids with each other, and resynthesis from primary precursors. The use of different methods of fixing and fermentation provides activation or inhibition of these processes, thereby making it possible to carry out target-oriented correction of the alkaloid composition of the medicinal plants studied.     

Theoretical bases of optimization of the modes of postharvest treatment of alkaloid-synthesizing medicinal plants

The method of disks in combination with thin-layer chromatography and spectrophotometry was used for a comparative evaluation of the efficiency of different methods of fixing and fermentation of medicinal plants (leaves). Medicinal plant species capable of synthesizing alkaloids of various structural types (isoquinoline derivatives including benzophenanthridines, bisbenzylisoquinoline, quaternary protoberberines, and aporphines, as well as steroid and diterpene alkaloids) were used. The methods of fixing and fermentation were shown to exert a substantial effect on both the qualitative and quantitative composition of alkaloids. This difference in the alkaloid composition was found to represent the superposition of three independent and, to a large extent, opposite processes: catabolism of alkaloids, interaction of alkaloids with each other, and resynthesis from primary precursors. The use of different methods of fixing and fermentation provides activation or inhibition of these processes, thereby making it possible to carry out target-oriented correction of the alkaloid composition of the medicinal plants studied.     

Distribution of Benzylisoquinolines in Magnoliidae and Other Taxa

Based on the analysis of benzylisoquinoline alkaloids of 323 samples in 11 families, 50 genera and 181 species of the Chinese flora discussed in this paper are the biogenesis, evolution, distribution pattern and botanical sources as well as the pharmacological action of this specific category of alkaloids. Benzylisoquinoline alkaloids are found mainly in Magnoliidae, in which aporphines, bisbenzylisoquinolines and protoberberines are the three major types of the alkaloids. More specifically, aporphines appeare more concentrated in primitive woody plants such as the Annonaceae, while bisbenzylisoquinolines are especially common in the Menispermaceae, Thalictrum (the Ranunculaceae) and Berberis (the Berberidaceae). As to protoberberines, the quaternary ones occur mainly in the families Ranunculaceae and Berberidaceae, whereas the tertiary ones mainly in the relatively advanced families Menispermaceae and Papaveraceae within Magnoliidae. As a whole, a general rule can be drawn that the simpler the chemical structure of the benzylisoquinolines is, the more widely they are distributed in primitive groups; more specific ones only have a limited distribution in more advanced groups or even within one family or one to several genera. This general pattern of distribution of benzylisoquinoline alkaloids in plants may be of value as a taxonomic criterion for plant systematics. Furthermore, this group of alkaloids covers the gamut of pharmacologic responses, such as the antibacterial effect and the effect to cardiovascular and nervous systems, and consequently the correlation between benzylisoquinoline alkaloids and their pharmacologicactivities within Magnoliidae may worthily be applied for the finding of new drugs.     

Isoquinoline alkaloids

Representatives of eleven different classes of isoquinoline alkaloids inhibit Na⁺, K⁺-ATPase and Mg²⁺-ATPase in rat brain microsomal preparations. In most cases the Na⁺, K⁺-ATPase is more sensitive than Mg²⁺-ATPase to inhibition by the alkaloids. The classes of alkaloids can be ranked according to potency of inhibition of Na⁺, K⁺-ATPase. Protoberberines are most effective, followed in decreasing order by benzophenanthridines, benzylisoquinolines, aporphines, tetrahydroprotoberberines, pavines, protopines, isoquinolines, tetrahydrobenzylisoquinolines, morphinanes, and tetrahydroisoquinolines. As specific representatives of each of the first four classes of alkaloids, berberine, sanguinarine, papaveroline and 1,2,10,11-tetrahydroxyaporphine, respectively, prove most valuable in kinetic studies because they exhibit the greatest inhibitory action on brain Na⁺, K⁺-ATPase. Kinetic analyses plotted in double reciprocal form reveal that berberine and 1,2,10,11-tetrahydroxyaporphine are simple linear competitive inhibitors with respect to ATP, whereas sanguinarine and papaveroline are simple linear noncompetitive inhibitors. These four representative alkaloids exhibit nonlinear competitive inhibition with respect to Na⁺-activation. Additionally, these alkaloids significantly inhibit rat brain microsomal K⁺-activatedpNPPase. The results demonstrate that certain members of several classes of isoquinoline alkaloids markedly affect various cation-dependent phosphohydrolases in vitro.     

Genetic Aspects of the Relationship between Isoquinoline Alkaloids and Mineral Elements in Greater Celandine (Chelidonium majus L.)

Interrelations between the total content of isoquinoline alkaloids, the concentrations of quaternary protoberberines and benzophenanthridines, and the amount of K, Cu, Co, Al, Ba, and Zn in aerial parts of individual celandine plants were revealed, within a single cenopopulation, using correlation analysis and regression analysis. Mathematical models describing the regulation of isoquinoline metabolism by some of the mineral elements were obtained in analytical form. The results suggest that this process is genetically determined.     

Genetic aspects of the relationship between isoquinoline alkaloids and mineral elements in greater celandine (Chelidonium majus L.)

Interrelations between the total content of isoquinoline alkaloids, concentrations of quaternary protoberberines and benzophenanthridines, and the amount of K, Cu, Co, Al, Ba, and Zn in aerial parts of individual celandine plants were revealed, within a single cenopopulation, using correlation analysis and regression analysis. Mathematical models describing the regulation of isoquinoline metabolism by some of the mineral elements were obtained in the analytical form. The results suggest that this process is genetically determined.     

Effects of flavonoids on nonenzymatic lipid peroxidation: structure-activity relationship

The in vitro effects of several flavonoids on nonenzymatic lipid peroxidation in the rat brain mitochondria was studied. The lipid peroxidation was indexed by measuring the MDA production using the 2-thiobarbituric acid TBA test. The flavonoids, apigenin, flavone, flavanone, hesperidin, naringin, and tangeretin promoted the ascorbic acid-induced lipid peroxidation, the extent of which depended upon the concentration of the flavonoid and ascorbic acid. The other flavonoids studied, viz., quercetin, quercetrin, rutin, taxifolin, myricetin, myricetrin, phloretin, phloridzin, diosmetin, diosmin, apiin, hesperetin, naringenin, (+)-catechin, morin, fisetin, chrysin, and 3-hydroxyflavone, all showed varying extents of inhibition of the nonenzymatic lipid peroxidation, induced by either ascorbic acid or ferrous sulfate. The flavonoid aglycones were more potent in their antiperoxidative action than their corresponding glycosides. Structure-activity analysis revealed that the flavonoid molecule with polyhydroxylated substitutions on rings A and B, a 2,3-double bond, a free 3-hydroxyl substitution and a 4-keto moiety, would confer upon the compound potent antiperoxidative properties.     

Potential cancer chemopreventive activity of simple isoquinolines, 1-benzylisoquinolines, and protoberberines

Seventeen simple isoquinolines, 15 1-benzylisoquinolines, and 19 protoberberines were tested for their inhibitory activities against Epstein-Barr virus early antigen (EBV-EA) activation induced by 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Among the tested alkaloids, the inhibitory activity of all 1-benzylisoquinolines and 11 protoberberines was higher than that of beta-carotene. The 1-benzylisoquinolines 19, 21, 22, 29, and 34 and protoberberines 41, 47-49, 51, 52, and 55 showed potent inhibitory effects on EBV-EA induction (96-100% inhibition at 1 x 10(3) mol ratio/TPA). These alkaloids were more active than the naturally occurring alkaloids, 23, 25, 33, 53, and 54. In addition, fifteen simple isoquinolines, eighteen 1-benzylisoquinolines and eight protoberberines were evaluated with respect to their ability to scavenge 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radicals. Nine simple isoquinolines, ten 1-benzylisoquinolines, and four protoberberines were more potent than alpha-tocopherol, and four 1-benzylisoquinolines, 20 and 28-30, exhibited potent activities (SC50 4.5-5.8 microM). Their activities were higher than the naturally occurring alkaloids, 23, 25, and 33. Therefore, some of the isoquinoline alkaloids indicating the high activity on both assays may be potentially valuable cancer chemopreventive agents. Structure-activity relationships are discussed for both tests.     

Propranolol as xanthine oxidase inhibitor: implications for antioxidant activity

Propranolol is the beta-blocker most widely used in the management of cardiovascular disorders. It has been proposed that propranolol may act as a "chain-breaking" antioxidant. We have directly examined the ability of propranolol to inhibit superoxide-dependent, iron-promoted cardiac membrane phospholipid peroxidation, with xanthine oxidase (XOD) as a physiologically-recognized, enzymatic superoxide generator. Our results demonstrate that propranolol not only protects cardiac-membrane lipid from peroxidative damage, but also acts as a simple, reversible XOD inhibitor, noncompetitive with xanthine substrate. Propranolol, at effective antiperoxidant and XOD-inhibitory concentrations, cannot scavenge superoxide radical. The antiperoxidative profile of propranolol resembles that of the known XOD inhibitor allopurinol, although allopurinol, a tight-binding substrate-analog competitive with xanthine, inhibits XOD in a manner mechanistically very different from that of propranolol. Furthermore, the antiperoxidative profiles of both propranolol and allopurinol do not resemble those of chain-breaking antioxidants such as alpha-tocopherol. These data, along with the tendency of propranolol to concentrate in myocardial membranes and cytosol, suggest that the observed antioxidant action of propranolol, as a consequence of XOD inhibition, could play a pharmacologic role in propranolol's cardioprotective effects.     

Antidiabetic and antioxidative effects of Annona squamosa leaves are possibly mediated through quercetin-3-O-glucoside

Present investigation was made to reveal the involvement of a quercetin in the antidiabetic and antiperoxidative effects of Annona squamosa leaf extract. Quercetin-3-O-glucoside (characterized by UV, IR, MS and NMR analyses) was isolated from Annona squamosa leaves and examined for its potential to regulate alloxan-induced hyperglycemia and lipid peroxidation (LPO) in rats. While in alloxan treated animals, an increase in the concentration of serum glucose with a parallel decrease in insulin level was observed, administration of 15 mg/kg/day of isolated quercetin-3-O-glucoside for 10 consecutive days to the hyperglycemic animals reversed these effects and simultaneously inhibited the activity of hepatic glucose-6-phosphatase. It further decreased the hepatic and renal LPO with a concomitant increase in the activities of antioxidative enzymes, such as catalase (CAT) and superoxide dismutase (SOD) and in glutathione (GSH) content, indicating its safe and antiperoxidative effects. These findings suggest the potential of quercetin-3-O-glucoside in the amelioration of diabetes mellitus and tissue lipid peroxidation. It also appears that the antidiabetic effects of A. squamosa leaf extract is possibly mediated through the insulin stimulating and/or free radical scavenging properties of its active constituent, quercetin-3-O-glucoside.     

Preventive effects of Cassia auriculata L. flowers on brain lipid peroxidation in rats treated with streptozotocin

The effect of aqueous extract of the flowers of Cassia auriculata were examined on antioxidants and lipid peroxidation in the brain of streptozotocin diabetic rats. Significant increase in the activities of superoxide dismutase, catalase, glutathione peroxidase, glutathione-S-transferase and reduced glutathione were observed in brain on treatment with Cassia auriculata flower extract (CFEt) and glibenclamide. Both the treated groups showed significant decrease in thiobarbituric reactive substances (TBARS) and hydroperoxide formation in brain, suggesting its role in protection against lipid peroxidation induced membrane damage. Since the study of induction of the antioxidant enzymes is considered to be a reliable marker for evaluating the antiperoxidative efficacy of medicinal plant, these findings are suggestions of possible antiperoxidative role played by Cassia auriculata flower extract.     

Dietary chitosan supplementation attenuates isoprenaline-induced oxidative stress in rat myocardium

Despite considerable advances in diagnosis and management over the last three decades, acute myocardial infarction continues to be a major public health problem. It is predicted that ischemic heart diseases will constitute the major disease-burden worldwide in the year 2020. In the present study, an attempt has been made to examine the effects of dietary chitosan supplementation on lipid peroxidation and cardiac antioxidant defense system in isoprenaline-induced myocardial infarction in rats, an animal model of myocardial infarction in man. Dietary chitosan intake significantly attenuated the isoprenaline-induced lipid peroxidation and maintained the level of reduced glutathione at near normal. Its administration demonstrated an antioxidant effect by maintaining the activities of myocardial glutathione dependent antioxidant enzymes (glutathione peroxidase and glutathione-S-transferase) and antiperoxidative enzymes (superoxide dismutase and catalase) at levels comparable to that of controls. The results of the present study indicate that the salubrious effects of dietary supplementation of chitosan is probably related to a counteraction of free radicals and/or to normal maintenance of the activities of free radical enzymes and the level of GSH, which protect myocardial membrane against oxidative damage by decreasing lipid peroxidation.     

Role of zinc on lipid peroxidation and antioxidative enzymes in intestines of ethanol-fed rats

This study was undertaken to investigate the effects of zinc on lipid peroxidation and various antioxidative enzymes in the intestines of male Wistar rats fed on ethanol. It was observed that NADPH-dependent lipid peroxidation (LP) was significantly increased upon ethanol treatment for 4 and 8 wk. The concentraton of glutathione as well as the activities of catalase, superoxide dismutase (SOD), glutathione peroxidase (GPx), and glutathione reductase (GR) were also found to be significantly increased upon ethanol feeding at all of the treatment intervals. The glutathione levels were found to be further elevated upon combined zinc and ethanol treatments. Interestingly, the administration of zinc to ethanol-fed rats was able to bring down the elevated levels of LP, catalase, SOD, and GPx, thus indicating the antiperoxidative potential of zinc under such conditions.     

Preconditioning with diosgenin and treadmill exercise preserves the cardiac toxicity of isoproterenol in rats

This study was aimed to evaluate the preventive effect of diosgenin and exercise on tissue antioxidant status in isoproterenol-induced myocardial infarction (MI) in male Wistar rats. Levels of lipid peroxides, reduced glutathione (GSH), and the activities of glutathione-dependent antioxidant enzymes (glutathione peroxidise and glutathione reductase) and antiperoxidative enzymes (catalase and superoxide dismutase) in the plasma and the heart tissue of experimental groups of rats were determined. Pretreatment with diosgenin and exercise exerted an antioxidant effect against isoproterenol-induced myocardial infarction by blocking the induction of lipid peroxidation. A tendency to prevent the isoproterenol-induced alterations in the level of GSH, in the activities of glutathione-dependent antioxidant enzymes and antiperoxidative enzymes was also observed. Histopathological findings of the myocardial tissue showed a protective role for combination of diosgenin and exercise in isoproterenol (ISO)-treated rats. Thus, the present study reveals that preconditioning with diosgenin and exercise exerts cardioprotective effect against ISO-induced MI due to its free radical scavenging and antioxidant effects, which maintains the tissue defense system against myocardial damage.     

Simple isoquinoline and benzylisoquinoline alkaloids as potential antimicrobial, antimalarial, cytotoxic, and anti-HIV agents

Twenty-six simple isoquinolines and 21 benzylisoquinolines were tested for antimicrobial, antimalarial, cytotoxic, and anti-HIV activities. Some simple isoquinoline alkaloids were significantly active in each assay, and may be useful as lead compounds for developing potential chemotherapeutic agents. These compounds include 13 (antimicrobial), 25, 26, and 42 (antimalarial), 13 and 25 (cytotoxic), and 28 and 29 (anti-HIV). A quaternary nitrogen atom of isoquinolium or dihydroisoquinolinium type may contribute to enhanced potency in the first three types of activities. In contrast, anti-HIV activity was found with tetrahydroisoquinoline and 6,7-dihydroxyisoquinolium salts.     

Antidiabetic potential of Citrus sinensis and Punica granatum peel extracts in alloxan treated male mice

An investigation on the effects of four different concentrations of peel extract from Citrus sinensis (CS) or Punica granatum (PG) in male mice revealed the maximum glucose lowering and antiperoxidative activities at 25 mg/kg of CS and 200 mg/kg of PG. In a separate experiment their potential was evaluated with respect to the regulation of alloxan induced diabetes mellitus. While a single dose of alloxan (120 mg/kg) increased the serum levels of glucose and alpha-amylase activity, rate of water consumption and lipid peroxidation (LPO) in hepatic, cardiac and renal tissues with a parallel decrease in serum insulin level, administration of 25 mg/kg of CS or 200 mg/kg of PG was found to normalize all the adverse changes induced by alloxan, revealing the antidiabetic and anti peroxidative potential of test fruit peel extracts. Subsequent phytochemical analysis indicated that the high content of total polyphenols in the test peels might be related to the antidiabetic and antiperoxidative effects of the test peels.     

Curcumin ameliorates oxidative stress during nicotine-induced lung toxicity in Wistar rats

Nicotine, a major toxic component of cigarette smoke has been identified as a major risk factor for lung related diseases. In the present study, we evaluated the protective effects of curcumin on lipid peroxidation and antioxidants status in bronchoalveolar lavage fluid (BALF) and bronchoalveolar lavage (BAL) of nicotine treated Wistar rats. Lung toxicity was induced by subcutaneous injection of nicotine at a dose of 2.5 mg/kg body weight (5 days a week, for 22 weeks) and curcumin (80 mg/kg body weight) was given simultaneously by intragastric intubation for 22 weeks. Measurement of biochemical marker enzymes: alkaline phosphatase, lactate dehydrogenase, lipid peroxidation and antioxidants were used to monitor the antiperoxidative effects of curcumin. The increased biochemical marker enzymes as well as lipid peroxides in BALF and BAL of nicotine treated rats was accompanied by a significant decrease in the levels of glutathione, glutathione peroxidase, superoxide dismutase and catalase. Administration of curcumin significantly lowered the biochemical marker enzymes, lipid peroxidation and enhanced the antioxidant status. The results of the present study suggest that curcumin exert its protective effect against nicotine-induced lung toxicity by modulating the biochemical marker enzymes, lipid peroxidation and augmenting antioxidant defense system.     

Antimalarials from nature

Malaria is a major public health problem mainly due to the development of resistance by the most lethal causative parasitic species, Plasmodium falciparum to the mainstay drugs like chloroquine. New drugs with unique structures and mechanism of action are urgently required to treat sensitive and drug-resistant strains of malaria. Historically, compounds containing novel structure from natural origin represent a major source for the discovery and development of new drugs for several diseases. This review presents recent advances in antimalarial drug discovery from natural sources, including plant extracts, and compounds isolated from plants, bacteria, fungi and marine organisms. These compounds offer new and novel scaffolds for development as antimalarials. The literature from 1998 to October 2008 is reviewed. The review present literature compilation from plant and marine extracts, alkaloids (naphthylisoquinolines, bisbenzylisoquinolines, protoberberines and aporphines, indoles, manzamines, and miscellaneous alkaloids) terpenes (sesquiterpenes, triterpenes, diterpenes, and miscellaneous terpenes) quassinoids, flavonoids, limonoids, chalcones, peptides, xanthones, quinones and coumarines, and miscellaneous antimalarials from nature. The review also provides an outlook to recent semisynthetic approaches to antimalarial drugs discovered from natural sources.     

Preparation of C-23 esterified silybin derivatives and evaluation of their lipid peroxidation inhibitory and DNA protective properties

A diverse series of C-23 esterified silybin derivatives (1a–n) were designed and synthesized. The antioxidative properties of these compounds were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and superoxide anion radical scavenging, ferrous ion chelation, and inhibition of rat liver homogenate lipid peroxidation. Their protective effects on the prevention of hydrogen peroxide induced DNA damage were also investigated. Most of the synthesized compounds exhibited more effective antioxidant activities than silybin. The esterified silybin analogues displayed satisfactory performance especially on iron chelation and antiperoxidative activity. Compound 1n in particular exhibited remarkable antiperoxidative effect with an IC₅₀ value of 0.2 ± 0.1 μM, which was stronger than that of quercetin (IC₅₀ = 1.8 ± 0.6 μM). Compounds 1c, 1e, 1g, 1h and 1k displayed potent, dose-dependent protective properties against DNA cleavage. The results of the bioassays support the antioxidative and DNA protective effects of these synthesized silybin derivatives.     

Studies on peroxidation processes of model membranes and synaptosomes: role of phosphatidic acid

Dipalmitoylphosphatidic acid (DPPA) was found to exert a strong inhibitory effect on Fe-induced peroxidation of arachidonic acid inserted into liposomal dipalmitoylphosphatidylcholine (DPPC) vesicles. This inhibition was quite effective both below and above the phase transition temperature of the liposomes. Moreover, we demonstrated the antiperoxidative activity of phosphatidic acid (PA) in synaptosomal membranes. PA enriched synaptosomes were prepared by the stimulation of the endogenous phospholipase D activity or by the incubation of the synaptosomes with Streptomyces chromofuscus phospholipase D. The possible contribution of PA to the in vivo defense mechanism against free radical-induced damage is discussed.