Hypericum caprifoliatum (Guttiferae) Cham. & Schltdl.: a species native to South Brazil with antidepressant-like activity

Medicinal Plants in the Treatment of Depression: Evidence from Preclinical Studies

Medicinal plants and their extracts are natural remedies with enormous potential for treating various diseases, including depression and anxiety. In the case of depression, hundreds of plants have traditionally been used in folk medicine for generations. Different plant extracts and natural products have been analyzed as potential antidepressant agents with validated models to test for antidepressant-like effects in animals, although other complementary studies have also been employed. Most of these studies focus on the possible mediators implicated in these potential effects, with dopamine, serotonin, and noradrenaline being the principal neurotransmitters implicated, both through interference with receptors and with their metabolism by monoamino oxidases, as well as through neuro-endocrine and neuroprotective effects. There are approximately 650 reports of antidepressant-like medicinal plants in PubMed; 155 of them have been compiled in this review, with a relevant group yielding positive results. Saffron and turmeric are the most relevant species studied in both preclinical and clinical studies; St. John's wort or kava have also been tested extensively. To the best of our knowledge, no review to date has provided a comprehensive understanding of the biomolecular mechanisms of action of these herbs or of whether their potential effects could have real benefits. The purpose of this narrative review is to provide an update regarding medicinal plants from the year 2000 to the present to examine the therapeutic potential of these antidepressant-like plants in order to contribute to the development of new therapeutic methods to alleviate the tremendous burden that depression causes worldwide.

Phytochemistry and pharmacology of anti-depressant medicinal plants: A review

Stress renders an individual to experience mental pressure and exhaustion which brings about feelings of anxiety, depression, anger and/or other negative emotions. Depression affects a person's state of mind, behaviour, health and is often associated with suicide. The use of anti-depressant drugs as therapeutic agents is associated with symptoms such as, delayed onset of action, side-effects, drug-drug and dietary interactions, sexual dysfunction, cardiac toxicity, etc. Thus, there is need to target these issues and improve current treatment options. Medicinal plants have long been used in discovering novel treatment strategies and compounds with promising roles in treating various disease conditions. There has been an increase, worldwide, in the use of medicinal plants and herbs for developing nutraceuticals for treatment of depression and other psychiatric disorders. Medicinal plants in their natural forms are valuable as they are rich in various phytochemical compounds. These phytochemical compounds have pharmacological roles in treating various diseases conditions; apart from being widely available in nature and commercially beneficial. The phytochemical compounds in plants are constantly being explored through various experimental studies to determine the molecular basis of how medicinal plants work in relation to drugs and diseases and to develop neutraceuticals for improving conditions. This review summarizes 110 medicinal plants and their phytochemical constituents that have been shown to possess anti-depressant activity. This review also highlights the various mechanisms of anti-depressant action of some of these plants and their plant parts like roots, stem, leaves, flowers, fruit or whole plant; phytochemical compounds showing anti-depressant activity such flavanoids, steroids, saponins, sugars, lectins, alkaloids, etc.; and various anti-depressant screening models used such as tail suspension test, forced swim test, chronic unpredictable stress test, sucrose preference test, monoamine oxidase inhibition assay, learned helplessness test, open field test, hole board test, etc. However, mechanistic evaluation of many of these plants still needs to be investigated and explored.

The protective effect of Hypericum connatum on stress-induced escape deficit in rat is related to its flavonoid content

Context Hypericum perforatum L. (Hypericaceae), used in moderate depression treatment, is active in experimental tests for antidepressant activity. For H. connatum Lam., a South American species lacking hyperforin, antidepressant effects have not been demonstrated. Objective This study evaluates the antidepressant-like effect of H. connatum in rats and identifies the components involved in this activity. Materials and methods First, the effects of acute and 14-d oral administrations of an extract derived from H. connatum aerial parts were studied using the Escape Deficit (ED) test. Next, methanol-extracted flavonoid-enriched fractions B and C and fraction-purified flavonoids (quercetin, rutin and isoquercitrin) were evaluated in the ED test after acute administration. To rule out possible confounding effects of the flavonoids, we examined nociceptive threshold using the tail-flick test and anxious behaviour using the elevated plus maze (EPM) test. Results Hypericum connatum increased reactivity of unavoidable stress-exposed rats after acute (0.5 and 1 g/kg: ED = 18.6/30 and 19.8/30, respectively) and repeated administration (0.5 g/kg twice daily: ED = 17.8/30). Protective effects were observed for fractions B and C (250 mg/kg: ED = 18.1/30 and 18.8/30, respectively), quercetin (2.5, 5 and 10 mg/kg: ED = 15.3/30, 18.3/30 and 21.6/30, respectively), rutin (5 and 10 mg/kg: ED = 15.4/30 and 13.0/30, respectively) and isoquercitrin (2.5 mg/kg: ED = 19.2/30). The flavonoids did not modify nociceptive threshold or performance in the EPM test. Discussion and conclusion Hypericum connatum showed protective activity in the ED test, a correlate of potential antidepressant-like effects that appeared to be related to the flavonoid components of this species.

Pharmacological basis for the use of Hypericum oblongifolium as a medicinal plant in the management of pain, inflammation and pyrexia

BACKGROUND

The present therapeutic agents for the treatment of pain, inflammation and pyrexia are not very effective and accompanied by various side effects. Therefore, new effective agents are the most wanted. The present study investigates the anti-nociceptive, anti-inflammatory and antipyretic activities of crude methanol extract of Hypericum oblongifolium.

METHODS

In vivo acetic acid induced writhing and hot plate tests were used for antinociceptive effects at 100, 200 and 300 mg/kg i.p. The anti-inflammatory and antipyretic potential of methanol extract were tested in carrageenan induced paw edema in mice and yeast induced hyperthermia respectively.

RESULTS

The extract doses of 100, 200 and 300 mg/kg i.p. revealed significant inhibitory effect (P < 0.001) in acetic acid induced writhing test. Pretreatment of extract at doses of 100, 200 and 300 mg/kg i.p. produced significant anti-inflammatory effect (P < 0.001) in the carrageenan induced paw edema. The methanol extract also showed significant antipyretic effect in yeast induced hyperthermia in mice during various assessment times.

CONCLUSIONS

The methanol extract of H. oblongifolium showed significant anti-nociceptive, anti-inflammatory and antipyretic effects in various animal models and thus validates the traditional uses of the plant in said conditions.

Uliginosin B, a natural phloroglucinol derivative, presents a multimediated antinociceptive effect in mice

Objective

Investigate the involvement of monoaminergic and glutamatergic systems on the antinociceptive and ataxic effects of uliginosin B, which we have already demonstrated to be a promising molecular scaffold to develop new analgesic drugs.

Methods

Uliginosin B was obtained from hexane extract of aerial parts of Hypericum polyanthemum by chromatographic methods. Uliginosin B antinociceptive and motor coordination effects were evaluated in mice by using hot-plate (15 and 90 mg/kg, i.p.) and rotarod (90 mg/kg, i.p.) tests, respectively. The mechanism of action was investigated through pretreatments with prazosin 1 mg/kg intraperitoneal (α1 receptor antagonist), yohimbine 5 mg/kg intraperitoneal (α2 receptor antagonist), pCPA 300 mg/kg intraperitoneal (serotonin synthesis inhibitor) and MK-801 0.25 mg/kg intraperitoneal (N-methyl-D-aspartic acid receptor antagonist).

Key findings

The antinociceptive effect of uliginosin B (15 and 90 mg/kg, i.p.) was reduced significantly by pCPA and MK-801. Prazosin and yohimbine improved the antinociceptive effect of the highest dose (90 mg/kg, i.p.) of uliginosin B only. The ataxic effect of uliginosin B (90 mg/kg, i.p.) was completely prevented by pretreatment with pCPA or MK-801, but it was unaffected by pretreatment with prazosin or yohimbine.

Conclusion

These data confirm the contribution of monoaminergic neurotransmission as well as provide the first evidence of glutamatergic neurotransmission contribution to the uliginosin B effects.

Uliginosin B presents antinociceptive effect mediated by dopaminergic and opioid systems in mice

Previous studies have shown that uliginosin B inhibits dopamine reuptake in rat brain. This compound occurs in Hypericum polyanthemum and H. caprifoliatum for which was reported to have antinociceptive effect sensitive to naloxone. The aim of this study was to assess the antinociceptive effect of uliginosin B and to evaluate the involvement of opioid and dopaminergic receptors activation. Uliginosin B presented antinociceptive effect in hot-plate and abdominal writhing tests, in mice, at doses that did not impair the motor coordination (15 mg/kg, i.p.). Uliginosin B in high dose (90 mg/kg, i.p.) presented ataxic effect in the rotarod apparatus. These effects seem to be mediated by distinct receptors since the effect on the hot-plate was completely abolished by naloxone and sulpiride, but it was unaffected by SCH 23390. On the other hand, the motor impairment induced by uliginosin B was completely prevented by naloxone and partially prevented by sulpiride and SCH 23390. However, the receptors' activation appears to be indirect since uliginosin B did not bind to opioid and dopaminergic receptors. Thus, uliginosin B effects probably are due to its ability to inhibit monoamine reuptake with consequent activation of dopamine receptors and indirect stimulation of opioid system.

Acute and repeated-doses (28 days) toxicity study of Hypericum polyanthemum Klotzsch ex Reichardt (Guttiferare) in mice

Hypericum polyanthemum, a South Brazilian species showed antidepressant-like and antinociceptive effects in rodents. Since limited information is available on the toxicity and safety profile of the Hypericum genus, we therefore investigated whether H. polyanthemum cyclo-hexane extract (POL) treatment could be associated with toxicity in preclinical setting using mice as an experimental model. These toxicity studies were based on the guidelines of the Organization for Economic Cooperation and Development (OECD-guidelines 423 and 407). Animals received POL single dose (2000 mg/kg, p.o.) or daily for 28-days (90, 450 and 900 mg/kg, p.o.). Acute toxicity study did not detect any clinical signs, changes in behavior or mortality. In repeated dose toxicity study, POL affected the body weight gain and induced biochemical, hematological and liver histological changes at 450 and 900 mg/kg. Mice treated with POL 90 mg/kg did not show any toxicity signs. In conclusion H. polyanthemum can be classified as safe (category 5) according to OECD acute toxicity parameters. However, the alterations observed after repeated treatment with high doses suggest that the liver could be the target organ on potential H. polyanthemum toxicity and point to the need of further toxicity studies.

Uliginosin B, a phloroglucinol derivative from Hypericum polyanthemum: a promising new molecular pattern for the development of antidepressant drugs

In this study we have demonstrated that cyclohexane extract of Hypericum polyanthemum (POL) and its main phloroglucinol derivative uliginosin B (ULI) present antidepressant-like activity in rodent forced swimming test (FST). The involvement of monoaminergic neurotransmission on the antidepressant-like activity of ULI was evaluated in vivo and in vitro. POL 90 mg/kg (p.o.) and ULI 10 mg/kg (p.o.) reduced the immobility time in the mice FST without altering locomotion activity in the open-field test. The combination of sub-effective doses of POL (45 mg/kg, p.o.) and ULI (5 mg/kg, p.o.) with sub-effective doses of imipramine (10 mg/kg, p.o.), bupropion (3 mg/kg, p.o.) and fluoxetine (15 mg/kg, p.o.) induced a significant reduction on immobility time in FST. The pretreatment with SCH 23390 (15 μg/kg, s.c., dopamine D1 receptor antagonist), sulpiride (50 mg/kg, i.p., dopamine D2 receptor antagonist), prazosin (1mg/kg, i.p., α1-adrenoceptor antagonist), yohimbine (1mg/kg, i.p., α2-adrenoceptor antagonist) and pCPA (100 mg/kg/day, i.p., p-chlorophenilalanine methyl ester, inhibitor of serotonin synthesis, for four consecutive days) before ULI administration (10 mg/kg, p.o.) significantly prevented the anti-immobility effect in FST. ULI was able to inhibit synaptosomal uptake of dopamine (IC50 = 90 ± 38 nM), serotonin (IC50 = 252 ± 13 nM) and noradrenaline (280 ± 48 nM), but it did not bind to any of the monoamine transporters. These data firstly demonstrated the antidepressant-like effect of POL and ULI, which depends on the activation of the monoaminergic neurotransmission in a different manner from the most antidepressants.

Antinociceptive Activity of Trichilia catigua Hydroalcoholic Extract: New Evidence on Its Dopaminergic Effects

Trichilia catigua is a native plant of Brazil; its barks are used by some local pharmaceutical companies to prepare tonic drinks, such as Catuama. The present study was addressed to evaluate the effects of T. catigua hydroalcoholic extract in mouse nociception behavioral models, and to evaluate the possible mechanisms involved in its actions. Male Swiss mice were submitted to hot-plate, writhing and von Frey tests, after oral treatment with T. catigua extract (200 mg kg⁻¹, p.o.). The extract displayed antinociceptive effect in all three models. For characterization of the mechanisms involved in the antinociceptive action of the extract, the following pharmacological treatments were done: naloxone (2.5 mg kg⁻¹, s.c.), SR141716A (10 mg kg⁻¹, i.p.), SCH23390 (15 μg kg⁻¹, i.p.), sulpiride (50 mg kg⁻¹, i.p.), prazosin (1 mg kg⁻¹, i.p.), bicuculline (1 mg kg⁻¹, i.p.) or dl-p-chlorophenylalanine methyl ester (PCPA, 100 mg kg⁻¹, i.p.). In these experiments, the action of T. catigua extract was evaluated in the hot-plate test. The treatment with SCH23390 completely prevented the antinociceptive effect, while naloxone partially prevented it. The possible involvement of the dopaminergic system in the actions of T. catigua extract was substantiated by data showing the potentiation of apomorphine-induced hypothermia and by the prevention of haloperidol-induced catalepsy. In conclusion, the antinociceptive effects of T. catigua extract seem to be mainly associated with the activation of dopaminergic system and, to a lesser extent, through interaction with opioid pathway.

Antidepressant-like effect of hyperfoliatin, a polyisoprenylated phloroglucinol derivative from Hypericum perfoliatum (Clusiaceae) is associated with an inhibition of neuronal monoamines uptake

This study investigated, in mice, the antidepressant like effect of hyperfoliatin, a prenylated phloroglucinol derivative isolated from the aerial parts of Hypericum perfoliatum, as well as its action on monoaminergic systems. In the forced-swimming test, hyperfoliatin dose-dependently reduced immobility time. Immobility was interpreted as an expression of "behavioural despair", which could be a component of depression syndrome. The effect of hyperfoliatin did not result from the stimulation of animal motor activity. Hyperfoliatin inhibited, in a concentration-dependent manner, the [(3)H]-dopamine, [(3)H]-serotonin and [(3)H]-noradrenaline synaptosomal uptakes, but did not prevent the binding of specific ligands to the monoamine transporters. These data suggest that the antidepressant-like effect of hyperfoliatin on the forced-swimming test is probably associated to monoamine uptake inhibition, due to a mechanism of action different from that of known antidepressants.