Pharmacological potentials of Premna integrifolia L.

Abstract

Premna integrifolia Linn. (Verbenaceae) is an important constituent of the formulation of ten roots of herbs known as Daśamūla and is widely used for treating various ailments in the Indian system of medicine. Aim of this review is to provide comprehensive information on the pharmacological activities of various parts of P. integrifolia. All the relevant universally accepted electronic databases were searched with respect to the terms “Agnimanthā”, “Headache tree”, “Premna integrifolia”, “Premna obtusifolia”, “Premna serratifolia” including Indian classical texts, pharmacopoeias, Ayurvedic books, journals, etc., for information without specific timeline. Complete information of the plant has been collected manually since the year 1964 and has been arranged chronologically. The collected data reflects that many ethno-medicinal claims have been confirmed through the modern in-vitro and in-vivo pharmacological studies using different extracts and their isolates of P. integrifolia. The isolation of active constituents, their biological actions, clinical safety and validation of traditional uses of P. integrifolia could provide leads for further scientific research. The information collected here will be useful to set-up research protocols for modern drugs and Ayurvedic formulation development.

INTRODUCTION

Medicinal plants are important for pharmacological research and drug development, not only when plant constituents are used directly as therapeutic agents, but also as starting materials for the synthesis of drugs or as models for pharmacologically active compounds.[1] India has a rich cultural heritage of traditional medicines which includes Ayurveda and Siddha system of medicines. Plants are the basic source of medicines in these systems.[2] A significant number of modern pharmaceutical drugs are thus based on or derived from medicinal plants.[3,4] Premna integrifolia is commonly known as Araṇi or Agnimanthā.[5,6] There is an inherent difference within the three Ayurvedic Formularies of India (AFIs) published with regard to the botanical sources of Agnimanthā.[7] The first edition (Part I) mentions Clerodendrum phlomidis Linn. as the authentic botanical source and Premna integrifolia Linn. as well as Premna mucronata Roxb. as substitutes.[8] However, in the second edition of Part I, P. integrifolia has been mentioned as the authentic plant source and C. phlomidis as well as P. mucronata are provided as the substitutes.[9] In Part II of the first edition of AFIs on the other hand, C. phlomidis. Linn. has been listed as the authentic Agnimanthā and Premna obtusifolia R. Br. as well as P. mucronata Roxb. are listed as the substitutes.[10] However, the basis for this variation in listing of botanical sources for Agnimanthā is not provided and hence not clear. Its root extract is an active ingredient of many Ayurvedic preparations such as, Ariṣṭam, Avaleham, Kvātham, Ghṛtam and Tailam.[11] This therapeutically important medicinal plant is not present in the Ayurvedic Pharmacopeia of India and it should be incorporated therein. It is also important to have the study of this plant incorporated into the syllabus of undergraduate and postgraduate pharmacy courses. P. integrifolia can be used as a good source of active therapeutics.[12] The present study provides the summary of up-to-date information on pharmacological activities of various parts of P. integrifolia.

SYNONYMS

Premna serratifolia L.; Premna obtusifolia R. Br.[11,13,14,15,16,17,18,19,20]

PHARMACOLOGICAL ACTIVITIES OF P. INTEGRIFOLIA

The reported pharmacological activities of P. integrifolia are described as follows and summary of the same is enlisted in Table 1.

Table 1.

Summary of reported pharmacological activities of Premna integrifolia

ANALGESIC/ANTINOCICEPTIVE

Analgesic activity was evaluated by using ethanolic extract of leaves of P. integrifolia. The activity was studied using acetic acid induced writhing model in mice. The extract produced 52.17% acetic acid induced writhing inhibition in mice at a dose of 500 mg/kg body weight, which is comparable to diclofenac sodium 65.21% at the dose of 25 mg/kg body weight.[21] Analgesic activity was also evaluated using methanolic extract of Premna integrifolia (MEPI) bark by writhing test in rats at doses 100 and 200 mg/kg body weight. The positive control group received Diclofenac-Na at the dose of 10 mg/kg p.o. The oral administration of both doses of MEPI significantly (P < 0.001) inhibited writhing response induced by acetic acid in a dose dependent manner. Antinociceptive study was performed by formalin induced pain model in rats at doses of 100 and 200 mg/kg body weight. The standard drug was used in the study is Indomethacin at 10 mg/kg, p.o. MEPI (100 and 200 mg/kg, p.o.) significantly (P < 0.001) suppressed the licking activity in either phase of the formalin-induced pain in rats in a dose dependent manner. But, MEPI, at the dose of 200 mg/kg body weight, showed the more licking activity against both phases of formalin-induced pain than that of the standard drug.[22]

ANTI-ARTHRITIC

Anti-arthritic activity was evaluated using ethanol extract of P. serratifolia wood by Freund's adjuvant induced arthritis model. Loss in body weight during arthritis was corrected on treatment with the said ethanol extract and standard drug, indomethacin. Biochemical parameters such as hemoglobin content, total WBC, RBC, erythrocyte and sedimentation rate were also estimated. The ethanol extract at the dose of 300 mg/kg body weight inhibited the rat paw edema by 68.32% which is comparable with standard drug indomethacin's 74.87% inhibition of rat paw edema after 21 days. Hence, it can be concluded that the ethanol extract of P. serratifolia wood possessed significant anti-arthritic activity against adjuvant induced arthritis.[23]

ANTIBACTERIAL

Antibacterial activity of ethanolic extract of leaves of P. integrifolia was tested by using the disc diffusion method. The extract showed significant antibacterial activity against both gram positive and gram negative bacteria.[17] Alcoholic extract of the root bark of P. integrifolia showed good antibacterial activity against gram-positive organisms during preliminary screening.[24] The oil (15 µL per disk) and extracts (300 µL per disk) of P. integrifolia displayed a great potential of antibacterial activity against Sarcina lutea (IFO 3232), Bacillus subtilis (IFO 3026), Escherichia coli (IFO 3007), Pseudomonas sp. (ATCC 13867), Klebsiella pneumonia (ATCC10031) and Xanthomonas campestries (IAM1671) with their respective zones of inhibition of 12.0 ± 1.2 to 22.1 ± 1.2 mm and MIC values of 62.5–250 µg per ml. The results of this study suggest that the natural products derived from P. integrifolia may have potential use in food, pharmaceutical and/or agro industries for preservatives or antimicrobial agents.[25]

ANTICANCER/ANTITUMOR/TUMOR SUPPRESSION/CYTOTOXICITY

Anticancer activity of biosynthesized silver nanoparticles (AgNps) using the ethanolic leaf extract of P. serratifolia was evaluated against carbon tetra chloride (CCl₄) induced liver cancer in Swiss albino mice (Balb/c). The synthesized silver nanoparticles were characterized by SEM, FTIR and XRD analyses. The Debye–Scherrer equation was used to calculate particle size and the average size of silver nanoparticles synthesized from P. serratifolia leaf extract was 22.97 nm. The typical pattern revealed that the sample contained cubic structure of silver nanoparticles. FTIR analysis confirmed that the bioreduction of silver ions to silver nanoparticles is due to reduction by capping material of the plant extract. Mice were divided into 5 groups of 6 animals each to evaluate the anticancer activity of synthesized silver nanoparticles. Group I: Normal control mice (healthy mice); Group II: Animals were treated with intraperitoneal injection of 50% CCl₄ in olive oil twice a week for 6 weeks to induce liver cancer; Group III: Liver cancer induced mice treated with P. serratifolia leaf extract (500 mg/kg) for 15 days; Group IV: Liver cancer induced mice treated with synthesized AgNps coated with P. serratifolia leaf extract (500 mg/Kg) for 15 days; Group V: Liver cancer induced mice treated with standard amino acid, isoleucine (3 g/d) for 15 days. After the experimental duration, blood serum and plasma samples from control and cancer induced animals were collected for biochemical analysis. The body mass of mice decreased after the liver cancer developed. The mice treated with P. serratifolia leaf extract and isoleucine amino acid regained their body mass. When compared with plant extract and amino acid treated mice, AgNps coated with P. serratifolia leaf extract treated mice regained the body mass nearer to control. The level of SGOT, SGPT and total protein in experimental mice in each group was significantly increased in CCl₄-induced liver cancerous mice when compared to control groups. The treatment of AgNps of P. serratifolia powder extract significantly restrained the level of SGOT, SGPT and total protein nearer to control in comparison to liver cancer mice treated with P. serratifolia leaf powder extract + isoleucine. There was a significant decrease in plasma thiobarbituric acid-reactive substances (TBARS) level in CCl4-induced liver cancerous mice when compared to control groups. The treatment of mice with AgNps coated with P. serratifolia leaf extract significantly restrained the level of plasma TBARS nearer to control when compared to liver cancerous mice treated with P. serratifolia leaf extract + isoleucine. The silver nanoparticles of P. serratifolia leaf extract were effective in treating liver cancer in Swiss albino mice when compared to P. serratifolia leaf extract with isoleucine.[26] Antitumor activity of P. integrifolia was evaluated using ethanolic extract on ehrlich ascites carcinoma cell lines. Tumor was induced intraperitoneally using Ehrlich Ascites carcinoma cells (1 × 10⁶ cells/mouse). Ethanolic extract of P. integrifolia was administered at a dose level of 100 and 200 mg/kg bw/day for 14 days to the experimental animals after 24 hr of tumor inoculation. The antitumor effect of EEPI was assessed by studying the parameters such as tumor volume, PCV, viable and non-viable cell counts, life span, hematological and glycoprotein profiles. Administration of EEPI decreased the ascites fluid volume, PCV and viable cell counts and increased the mean survival time of tumor bearing animals. The EEPI brought back the altered levels of hematological parameters and glycoprotein levels in a dose dependent manner in EAC bearing mice. The results obtained were comparable with the standard drug 5-Flurouracil (20 mg/kg. bw.). The data of the results of this study indicated that altered levels of glycoprotein content and hematological parameters due to EAC induction were brought back to near normal values after oral administration of ethanolic extract of P. integrifolia.[27] Tumor cell suppression potential was determined in three different cancer cell lines MCF7 (Breast cancer), HepG2 (Liver cancer) and A549 (Lung cancer) by SRB assay. The IC₅₀ value shows that the efficacy was dose dependent. The GI₅₀, TGI, LC₅₀ values were determined against each cell line and compared with the standard drug adriyamycin.[28] The methanolic extracts of leaves, root barks (RB) and root wood of P. serratifolia for cytotoxic activity against two cancer cell lines, i.e. SHSY-5Y neuroblastoma and B16 melanoma cells. Cell viability was assessed by measuring the fluorescence of Alamar Blue™ as described previously by Habtemariam and Jackson. The RB extract that showed promising activity was fractionated using solvents of increasing polarity followed by a combination of Sephadex LH-20 column and Combiflash chromatography as well as HPLC to extract the active principle. Comprehensive spectroscopic analysis including 1D and 2D NMR (COSY, HMQC, HMBC, NOESY) and MS analysis revealed the identity of the isolated compound as 11,12,16-trihydroxy-2-oxo-5-methyl-10-demethyl-abieta-1,10,6,8,11,13-pentene that appears to be a novel compound based on a new diterpene skeleton. The cytotoxic activity of the isolated compound was 21 and 23 times higher than the crude extract against the SHSY-5Yand B16 cells, respectively.[29] In-vitro cytotoxic activity of alcoholic extract of leaves of P. serratifolia was studied by tryphane blue exclusion method using EAC cell lines. Alcoholic extract had an IC₅₀ value of 75 μg/ml which indicates significant in-vitro cytotoxic activity of the extract. It is concluded that the alcoholic extract of leaves of P. serratifolia possessed significant antitumor activity.[30] Cytotoxicity screening of P. serratifolia leaves extract and their fractions (F1, F2, F3 and F4) were studied by brine shrimp lethality (BSL) bioassay. Among these, F1, F2 and F3 fractions of P. serratifolia have shown significant cytotoxicity, i.e. LC₅₀ values 7.61, 4.01, and 10.91 respectively as compared with those of the control. (Lethal concentration (LC₅₀) <100 ppm). P. serratifolia leaves extract and their fractions (F1, F2 and F3) that showed significant cytotoxicity were evaluated for total phenolic content (TPC) by using Folin-Ciocalteu reagent. TPC was found to be significantly higher i.e. 39.11 mg gallic acid equivalent (GAE)/g. Hence, the cytotoxicity screening system validates anticancer use of the plant by traditional healers and literature claims.[31]

ANTI-INFLAMMATORY

Anti-inflammatory activity of methanolic extract of Premna integrifolia (MEPI) bark was evaluated using carrageenan induced inflammatory model in rats at doses 100 and 200 mg/kg b. w. The standard drug was Indomethacin at 10 mg/kg, p.o. MEPI showed remarkable anti-inflammatory effects at 200 mg/kg dose, i.e. 71.16% inhibition, whereas standard Indomethacin showed 75.72% of inhibition of paw edema.[22] Anti-inflammatory activity of premnazole alkaloid isolated from P. integrifolia was demonstrated by using reducing pellet induced granuloma formation in rats.[32] However, preliminary anti-inflammatory and anti-arthritic activities were also studied.[33] The administration of the root extract inhibited the carrageenan induced acute paw oedema and formalin induced chronic paw oedema in a dose dependent manner. The animals treated with 70% methonolic extract at 250 mg/kg and 500 mg/kg showed 47.05 and 70.58% inhibition of carrageenan induced acute inflammation. In the case of formalin induced chronic inflammation, 250 mg/kg and 500 mg/kg showed inhibition of 50.00 and 72.00%, respectively.[34] The root and root callus extracts of P. serratifolia augments its anti-inflammatory activity against carrageenan induced paw edema. The results of a study proved the anti-inflammatory effect of callus derived luteolin through its biologically active components, which may worth for further investigation and elucidation.[35] Anti-inflammatory activity was evaluated by pretreatment with a single dose of methanolic extract of P. integrifolia (PIM) (300 mg/kg b.w.). The extract showed significant inhibition on carrageenan-induced rat hind paw edema, histamine induced wheal formation and acetic acid-induced mouse vascular permeation. The extract also showed significant inhibition of cyclo-oxygenase (COX-I) activity on rat uterus and plasma membrane stabilization. The results scientifically demonstrated the anti-inflammatory activity of P. integrifolia roots in various experimental models probably through their antihistaminic, antikinin, COX-inhibitory and antioxidant action.[36]

ANTIMICROBIAL

Antimicrobial activity was evaluated against the selected human pathogens (Bacillus sp., Enterococcus faecalis, E. coli, Klebsiella pneumoniae, Non-haemolytic Streptococci, Streptococcus epidermidis, Pseudomonas aeruginosa, Salmonella typhimurium) by using natural leaves, roots and its respective calli induced with help of various plant growth regulators. Results revealed increased inhibitory activities of callus extracts. The activities were found to be better when compared to the natural plant material extracts.[37] P. serratifolia was screened to evaluate in-vitro antimicrobial activity against the selected human pathogenic organisms. Findings showed potential antimicrobial properties of the extracts (133.33 mg/ml) and fractions (33.33 mg/ml) of root of P. serratifolia against the different bacterial organisms and fungi tested. The zones of inhibition of the extracts and fractions were comparable with that of standard antibiotics. The study suggests the plant to be promising for the development of antimicrobial phytomedicines. This also indicates its potential usefulness in the treatment of various pathogenic diseases with reduced toxicity and adverse effects when compared to synthetic chemotherapeutic agents.[38] The antimicrobial activity of different extracts of bark and wood of P. serratifolia was also studied against nine bacterial and four fungal organisms by disc diffusion method. Ethyl acetate, ethanol and aqueous extracts exhibited significant antibacterial activity, n-hexane and chloroform extracts exhibited moderate antibacterial activity and all the five extracts exhibited significant antifungal activity. Results revealed that all the extracts possessed a significant broad spectrum of antimicrobial activity when compared to ciprofloxacin and amphotericin-B. This may be due to the presence of phytoconstituents such as alkaloids, irridoid glycosides and flavonoids present in it.[39]

ANTI-OBESITY/HYPOLIPIDEMIC

Anti-obesity activity of chloroform-methanol (1:1) extract of P. integrifolia (CMPI) in mice fed with cafeteria diet was evaluated. In the cafeteria diet group there was significant increase in body weight, BMI, LIO, food consumption, organ weight (liver and small intestine), organ fat pad weight (mesenteric and peri-renal fat pad) and in the levels of serum glucose, triglyceride, total cholesterol, LDL and VLDL with a significant decrease in locomotor behavior (ambulation, rearing, grooming) and HDL levels. Animals treated with CMPI showed dose dependent activity. P. integrifolia (200 mg/kg) supplementation attenuated all the above alterations, which indicates the anti-obesity activity. The findings suggest that CMPIpossesses anti-obesity activity that substantiates its ethno-medicinal use in the treatment of obesity.[40] The effect of aqueous enriched fraction of P. integrifolia root (AEFPIR) against cafeteria diet induced obesity in Swiss Albino Mice was studied. There was a significant decrease in body weight, BMI, food consumption and in the levels of serum glucose, triglyceride, total cholesterol, LDL, and VLDL with a significant increase in the level of HDL in mice treated with simvastatin and AEFPIR groups compared with cafeteria diet group. Mice treated with AEFPIR show dose dependent effect. The AEFPIR (400 mg/kg) supplementation attenuated all the above alterations, which indicates the protective effect against cafeteria diet induced obesity that was further confirmed by histopathological analysis.[41] Hypolipidemic activity was also evaluated using hypercholesterolemic rabbit model in comparison to the established hypolipidemic drug atorvastatin. Lipid profile which includes total cholesterol, triglyceride, LDL, VLDL, HDL, fasting blood glucose and body weight were measured (i) at baseline, (ii) after 6 weeks of cholesterol feeding and (iii) 12 weeks i.e. after 6 weeks of drug administration. There was no significant change in body weight from baseline in either group. The intergroup difference in body weight was statistically significant at 6 weeks but not at 12 weeks. Fasting blood glucose values showed a similar pattern of change. In fasting lipid profile, both TC and LDL showed a remarkable rise in both groups after 6 weeks of pure cholesterol feeding. Subsequently, after 6 weeks of treatment, the elevated cholesterol levels were significantly reduced both by test and control drugs. Changes in HDL, VLDL and TG were insignificant. Powdered bark of P. integrifolia is able to lower diet induced elevated serum cholesterol and LDL in rabbit model. The extent of reduction is comparable to the established lipid lowering drug atorvastatin.[42] Anti-hyperlipidemic activity of P. integrifolia was evaluated in an experimental animal model. High fat diet caused significant increase in serum cholesterol, triglyceride, VLDL, LDL and significant reduction in HDL level. Both P. integrifolia and atorvastatin treatment showed significant prevention in increased in serum cholesterol, triglyceride, LDL as compared to cholesterol control group. HDL level was significantly increased in both treated and standard control group as compared to cholesterol control group.[43] Anti-hyperlipidaemic activity of P. integrifolia on nicotine induced hyperlipidaemia was evaluated. Nicotine caused significant increase in the serum cholesterol, triglyceride, VLDL, LDL and significant reduction in HDL level. P. integrifolia and atorvastatin treatment showed significant prevention in increased serum cholesterol, triglyceride, LDL as compared to nicotine control group. While HDL level was significantly increased in treated and standard group as compared to Nicotine control group. From the above results, it is clear that P. integrifolia is an effective anti-hyperlipidemic agent.[44]

ANTIOXIDANT

Ethanolic extract of root and root derived callus extracts of P. serratifolia were investigated against paracetamol induced oxidative stress in blood of male albino rats. This investigation concluded that, ethanolic extract of root callus possess significant antioxidant activity, which can help to overcome paracetamol induced toxicity.[21] 1,1-Diphenyl-2-picrul-hydrazil (DPPH) antioxidant and hydrogen peroxide (H₂O₂) scavenging effects were studied using the method of Blois and Rajan et al. The results of antioxidant and radical scavenging activity of P. serratifolia leaf powder extract (1,000 µg) exhibited 73.5 ± 4.66 and 69.24 ± 3.97% of antioxidant and H₂O₂ radical scavenging activity, respectively, which revealed that the leaves of P. serratifolia possessed radical scavenging activity.[26] The free radical scavenging activity of P. serratifolia leaf has been evaluated in various in-vitro model systems. The study showed that the methanolic extract of plant has free radical scavenging activity against superoxide radical, nitric oxide radical, hydroxyl radical, DPPH radical, ABTS radical and inhibition of lipid peroxidation.[28] The isolated compound, 11,12,16-trihydroxy-2-oxo-5-methyl-10-demethyl-abieta-1,10,6,8,11,13-pentene that appears to be a novel compound based on a new diterpene skeleton also possesses in-vitro antioxidant effects as evidenced by the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging effect where an IC₅₀ value of 20.4 ± 1.3 μM was obtained. In comparison, the positive control, caffeic acid, showed an IC₅₀ value of 14.4 ± 1.6 μM.[29] Antioxidant properties of the plants were analyzed by determining the scavenging effects of free radicals such as superoxide, hydroxyl, nitric oxide and lipid peroxidation generated with in-vitro assay systems. Concentrations of methanolic extract that were needed for 50% of inhibition were as follows – superoxide: 180 μg/ml, hydroxyl: 156 mg/ml, nitric oxide: 79 μg/ml and lipid peroxides: 60 μg/ml.[34] Antioxidant activity of the extract of P. integrifolia was evaluated using the anti radical, superoxide scavenging, erythrocyte membrane stability, anti lipid peroxidation, hydroxyl radical scavenging, nitric oxide scavenging and reducing power (ferric thiocynate method and β-carotene bleaching test) assays. Methanolic extract of P. integrifolia showed significant anti-oxidant activity.[36] Antioxidant activity was evaluated by using methanolic extract of P. serratifolia leaf in paracetamol intoxicated rats. Antioxidant enzymes: SOD, CAT and glutathione were evaluated in the blood samples and as well as in the isolated tissue samples of liver, kidney and heart. The disease control group showed decreased levels of antioxidant enzymes in blood and tissue samples. But the elevated levels of SOD, CAT and glutathione were observed significantly in liver, kidney and heart tissue samples and blood samples of the extract administered groups. The activity was found to be dose dependent. The overall efficacy of the extract is comparable with the standard drug silymarine. The study revealed that the methanolic extract of P. serratifolia was found to have potential antioxidant activity in the animal model system.[45] Antioxidant activity and active principle of the root woody tissues were investigated. Antioxidant effect was monitored using the DPPH radical scavenging assay. Through the use of comprehensive spectroscopy studies, the isolated active antioxidant principle was identified as acteoside (verbacoside) which is about four times more active than the crude root wood extract.[46] Compounds called iridoids glycosides, namely, premnadimer, 4-hydroxyasarinin-1-O-glucopyranoside, 10-O-trans-p-coumaroylcatalpol, 4-hdroxy-E-globularinin, premnosidic acid and 10-O-trans-p-coumaroyl-6-O-l-rhamnopyranosyl catalpol have been isolated from the stem bark of P. integrifolia and were evaluated for their radical scavenging, ferric reducing antioxidant potential using DPPH, FRAP, reducing power and NO scavenging assays. Significant scavenging activity was observed in DPPH and NO assays. IC₅₀ values of compounds 10-O-trans-p-coumaroylcatalpol and 4-hdroxy-E-globularinin were 0.37 and 0.29 M/mL in DPPH free radical scavenging assay, respectively.[47] Antioxidant activity of the oil and various organic extracts of P. integrifolia leaves were examined using DPPH and superoxide radical scavenging activities assay. In the first case, the IC₅₀ value of the P. integrifolia essential oil was found to be 12.1 ± 1.1 μg/ml. Among the extracts, the strongest activity was exhibited by the ethyl acetate extract with an IC₅₀ value of 15.43 ± 1.7 μg/ml. In the superoxide radical scavenging activities assay, ethyl acetate extract was superior to all other extracts (IC₅₀ = 22.60 ± 1.5 μg/ml). Furthermore, the amount of total phenolic compounds was also determined as gallic acid equivalent. The results of this study suggest that the natural products derived from P. integrifolia may have potential use in food, pharmaceutical and/or cosmetic industries.[48] Methanolic extract of the roots was evaluated for its in-vitro antioxidant activity using the anti radical, superoxide scavenging, anti lipid peroxidation, hydroxyl radical scavenging and nitric oxide scavenging, assays. The extract showed significant anti-oxidant activity which is scientifically demonstrated the use of P. integrifolia as a potential source of natural antioxidant.[49] Chloroform: methanol (1:1) and aqueous extract of P. integrifolia (CMEPI and AEPI) roots were evaluated to check their beneficial effect on human leucocytes and erythrocytes against hydrogen peroxide (H₂O₂) induced oxidative damage. Catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione (GSH) and lipid peroxidation (LPO) enzyme levels were used to assess hydrogen peroxide induced oxidative damage. Results of these studies revealed that there was an increase in the CAT, SOD, GPx and reduction of the GSH and LPO levels in H₂O₂ group compared with control. P. integrifolia root extract treated groups showed reduction of CAT, SOD, GPx and increase in the GSH and LPO levels as compared with H₂O₂ group. Chloroform: methanol (1:1) extract of P. integrifolia was found to be more effective than the aqueous extract. These studies suggest that, the extracts of P. integrifolia root possesses beneficial effect on human leucocytes and erythrocytes against H₂O₂ induced oxidative damage which substantiates their use in ethnomedicine as an antioxidant. Observed effect can be attributed to the flavonoid and phenol contents in the plant.[50]

ANTIPARASITIC

Antiparasitic activity of a few New Caledonian medicinal plants were studied.[51] Twenty-nine extracts of 18 medicinal plants used in New Caledonia by traditional healers to treat inflammation, fever and in cicatrizing remedies were evaluated in-vitro against several parasites (Leishmania donovani, Trypanosoma brucei brucei, Trichomonas vaginalis and Caenorhabditis elegans). Among the selected plants, Scaevola balansae and P. serratifolia were the most active against Leishmania donovani with IC₅₀ values between 5 and 10 g/ml.

ANTIULCER/GASTRO PROTECTIVE

Antiulcer activity of ethanolic extract of leaves of P. serratifolia using aspirin induced ulcers at dose levels of 200 and 400 mg/kg compared with ranitidine as a standard drug. Results showed dose dependent decrease in ulcer index, gastric acid secretion, free acidity, total acidity and increased the pH of gastric juice in aspirin and extract treated group of animals. Histopathological studies revealed that high doses of P. serratifolia leaves prevented ulcer formation.[52]

CARDIAC STIMULANT/CARDIOPROTECTIVE

Cardiac stimulant activity of stem bark and stem-wood of P. integrifolia was evaluated by using Isolated Frog Heart Perfusion Technique. The ethanol extract of P. integrifolia produced significant positive ionotropic and negative chronotropic actions similar to that of digoxin on frog (Rana hexadactyla) heart and its effect was inhibited by nifedipine but not by propranolol. A significant decreased in membrane Na⁺ K⁺ ATPase and Mg2 + ATPase and increased in Ca2 + ATPase further confirmed its cardiotonic activity. Aqueous extract of stem-bark and stem-wood of P. serratifolia produced positive ionotropic and chronotropic effects similar to that of adrenaline and its effect was antagonized by propranolol and nifedipine. The results suggested that the ethanol extract of stem-bark and stem-wood of P. serratifolia produced cardiotonic effect and aqueous extract of stem-bark and stem-wood of P. serratifolia produced β-adrenergic effect.[53] Cardioprotective effect of ethanol extract of stem-bark and stem-wood of P. serratifolia were tested on isoproterenol induced experimental myocardial infarction in rats. The cardioprotection was confirmed by ECG study in rat heart, electrophoresis analysis of serum protein, serum A/G ratio, biochemical studies such as heart tissue proteins, glycogen, nucleic acids and blood glucose. Subcutaneous injection of isoproterenol (20 mg/100 g body weight in 0.1 ml saline) to rats for 2 consecutive days caused myocardial damage and was confirmed by elevation of ST segments in rat heart ECG pattern, reduction in serum electrophoresis protein bands and serum A/G ratio, increase in heart tissue proteins and nucleic acids, increase in blood glucose and decrease in heart tissue glycogen. Pretreatment with ethanol extract of stem-bark and stem-wood of P. serratifolia (100 mg/100g body weight in 0.2 ml of 5% gum acacia) for 28 days through intraperitoneal injection in isoproterenol administered rats resulted in cardiprotection as compared with myocardial infarcted rats. This confirms the cardioprotective effect of ethanol extract of stem-bark and stem-wood of P. serratifolia on isoproterenol induced myocardial infarction in rats. The protective myocardial effect may be due to the phytoconstituents such as iridoid glycosides, alkaloids, flavonoids and phenolic compounds.[54]

CNS DEPRESSANT

CNS depressant activity of methanolic extract of P. integrifolia (MEPI) bark was evaluated using hole cross and open field test in rats at doses 250 and 500 mg/kg b. w. The standard group received Diazepam at the dose of 1 mg/kg body weight orally. Results of the hole-cross and open-field test were significant for all dose levels and followed a dose-dependent response. The depressing effect in hole-cross test was most intense during the second (60 min) and third (90 min) observation periods.[22]

HEPATOPROTECTIVE

Hepatoprotective activity of alcoholic extract of leaves of P. serratifolia using carbon tetrachloride was studied. The degree of protection in hepatoprotective activity was measured by using biochemical parameters such as SGOT, SGPT, ALP, bilirubin and total protein. The results suggest that the alcoholic extract at the dose level of 250 mg/kg produced significant hepatoprotection by decreasing the activity of serum enzymes, bilirubin, and lipid peroxidation which is comparable to that of standard drug silymarine.[30] Hepatotoxicity induced by paracetamol (800 mg/kg) administration was studied. The significant hepatic damage elicited by the levels of hepato specific enzymes such as SGOT, SGPT, LDH and CAT were observed in a group treated with root callus extracts (250 and 500 mg/kg) compared with other groups which were treated with field grown root extracts (250 and 500 mg/kg). The effects of root callus extracts were comparable to that of standard drug, silymarine. Histopathological findings also suggested the root callus extracts of P. serratifolia preventing the development of chronic damage.[55]

HYPOGLYCEMIC

Hypoglycemic activity was evaluated using streptozotocin induced type 1 and type 2 diabetic rats.[56] Hypoglycemic activity was also evaluated using 95% ethanolic extract of leaves in alloxan induced diabetic rats. Steady diabetes was confirmed by noting urine sugar regularly and then measuring blood glucose values before starting the experiment. To confirm definite hypoglycemic effect, final blood glucose values of each sample were brought down closer to normal fasting level using different doses of the ethanolic extract. The results indicate that P. integrifolia showed definite blood glucose lowering effect within 1 week using 250 mg/kg double dose.[57]

IMMUNOMODULATORY

Immunomodulatory activity was evaluated by using methanol extract of root of P. integrifolia in BALB/c mice.[58] Oral administration of methanol extract (300 mg/kg × 7 days) in mice prior to immunization with sheep red blood cells resulted in a significant increase in haemagglutinating antibody titre, plaque forming cell assay and delayed type hypersensitivity to SRBS. P. integrifolia enhanced the non specific immune response in carbon clearance test and showed significant immunoprophylactic effect, when tested on E. coli induced abdominal sepsis.

LONGEVITY-PROMOTING

In modern times, there has been an increase in the use of plants or herbal constituents for the prevention of age-related disorders. 4-Hydroxy-E-globularinin (4-HEG) is an iridoid and a major component of P. integrifolia. The discovery of this component represents a break-through in geriatrics because of its longevity-promoting activity of 4-HEG in an animal model, Caenorhabditis elegans. 4-HEG (20 mM) enhanced the mean life span of worms by over 18.8% under normal culture conditions and also enhanced their survival under oxidative stress. The longevity-promoting activity was associated with reduced reactive oxygen species (ROS) levels and fat accumulation in the worms. Gene-specific mutant studies verified the role of ROS detoxification pathways and simultaneous nuclear translocation of DAF-16 in the 4-HEG-mediated effects. Quantitative real-time PCR estimations and observations of transcriptional reporters indicated that 4-HEG was able to up-regulate stress-inducible genes, viz., hsp-16.2 and sod-3. Thus, 4-HEG may serve as a lead compound for the development of important nutraceuticals preventing the aging process.[59] Aging, the major cause of several ailments has led to intense exploration of potential drugs that delay aging and its associated effects. An identified iridoid compound, 10-O-trans-p-Coumaroylcatalpol (OCC), a major ingredient of P. integrifolia, OCC which forms an important constituent of famous herbal formulation Daśamūla, a ten herb formulation, commonly used for its various medicinal properties. Employing model system Caenorhabditis elegans, the effect of OCC on life span, stress resistance, chemotaxis, level of reactive oxygen species (ROS) and on the aggregation of alpha synuclein was studied. OCC extended the mean life span of nematodes, increased their tolerance against chemical induced stress, improved the chemotaxis index and reduced the ROS content. Further, the aggregation of Parkinson's disease (PD) associated protein, alpha synuclein (asyn), was decreased when transgenic a-syn expressing worms were raised on OCC mixed diet. Authors extended the studies further to explore the possible genetic mechanism that mediates the observed effects of OCC. Employing the genetic knockout mutants TK22 [mev-1(kn1) III]; GR1307 [daf-16(mgDf50) I]; VC199 [sir-2.1(ok434) IV] and transgenic GFP expressing strain TJ356 [zls356; DAF-16:GFP], these studies revealed that the effects were mediated by daf-16 and not by sir-2.1 or mev-1. Results indicates that OCC has the ability to ameliorate a-syn aggregation, reduce oxidative stress and promote longevity in C. elegans viaactivation of longevity promoting transcription factor DAF-16. Thus, OCC may serve as a lead compound of plant origin for important nutraceutical intervention against aging and age associated PD.[60]

NEUROPROTECTIVE

Neuroprotective effects were evaluated by using roots of P. serratifolia in the experimental model of febrile seizure.[61]

CONCLUSIONS

The present review reveals P. integrifolia to possess analgesic/antinociceptive, anti-arthritic, antibacterial, anticancer/antitumor/cytotoxic/tumor suppression, anti-inflammatory, antimicrobial, anti-obesity/hypolipidemic, antioxidant, antiparasitic, antiulcer/gastro-protective, cardiac stimulant/cardioprotective, CNS depressant, hepatoprotective, hypoglycemic, immunomodulatory, longevity-promoting and neuroprotective activities. According to the literature, most of the pharmacological activities of P. integrifolia is investigated by using methanol and ethanol as extractive solvents. This solvent generally contains high quantity of phenols, flavonoids, amino acids, vitamins, carbohydrates, etc., phytoconstituents. The activities may be due to the presence of these phytocompounds in the extracts. Most of the times, leaves and roots were selected for evaluating pharmacological activities. This article is provides an ready accessible source for pharmacological activities of various parts of P. integrifolia plant. The isolation of active constituents, their biological actions, clinical safety and validation of traditional uses of P. integrifolia may provide leads for further scientific research. The present information will be useful for setting up of research protocols for modern drug and Ayurvedic formulation development in curing and treating various diseases, which can prove its efficacy as a novel source for new drug development.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.