Betelvine (Piper betle L.): A comprehensive insight into its ethnopharmacology, phytochemistry, and pharmacological, biomedical and therapeutic attributes

Abstract Piper betle L. (synonym: Piper betel Blanco), or betel vine, an economically and medicinally important cash crop, belongs to the family Piperaceae, often known as the green gold. The plant can be found all over the world and is cultivatedprimarily in South East Asian countries for its beautiful glossy heart‐shaped leaves, which are chewed or consumed as betelquidand widely used in Chinese and Indian folk medicine, as carminative, stimulant,astringent, against parasitic worms, conjunctivitis, rheumatism, wound, etc., andis also used for religious purposes. Hydroxychavicol is the most important bioactive compound among the wide range of phytoconstituents found in essential oil and extracts. The pharmacological attributes of P. betle are antiproliferation, anticancer, neuropharmacological, analgesic, antioxidant, antiulcerogenic, hepatoprotective, antifertility, antibacterial, antifungal and many more. Immense attention has been paid to nanoformulations and their applications. The application of P. betle did not show cytotoxicity in preclinical experiments, suggesting that it could serve as a promising therapeutic candidate for different diseases. The present review comprehensively summarizes the botanical description, geographical distribution, economic value and cultivation, ethnobotanical uses, preclinical pharmacological properties with insights of toxicological, clinical efficacy, and safety of P. betle. The findings suggest that P. betle represents an orally active and safe natural agent that exhibits great therapeutic potential for managing various human medical conditions. However, further research is needed to elucidate its underlying molecular mechanisms of action, clinical aspects, structure–activity relationships, bioavailability and synergistic interactions with other drugs.


| INTRODUC TI ON
Bangladesh. 6 The most common varieties of betel are Magadhi, Salem, Mysore, Bangla, Kauri, Venmony, Meetha, Kapoori, Sanchi, Banarasi, Desavari, Kasi, Ghanagete and Bagerhati, which are mainly based upon their colour, aroma, taste and size. 1 P. betle is known by various names in different countries around used globe, though 'Paan' is the most used in India, Pakistan, Nepal and Bangladesh. 7 The betel leaf and areca nuts play a central role in Hindu culture as they are used in a variety of social, cultural and religious ceremonies. 1 Betel quid is a common practice in many countries because it acts as a natural tonic and mouth refresher to prevent oral malodour.

| D IS TRIBUTI ON AND CULTIVATI ON
The betel vine is believed to have originated in Malaysia. 38 The plant is widely grown in forests that are generally damp and also in hot and  Bengal. 43 Various types of Piper betle are found across the world, for instance, Magadhi, Kauri, Meetha, Salem, Venmony, Bangla, Banarasi, Kapoori, Kasi, Sanchi, Mysore, Desavari, Ghanagete and Bagerhati according to their size, colour and aroma. 44 Piper betle is generally propagated asexually by cutting stems rather than germinating seeds. 45 It needs a compatible tree or long support for its creeping habit. Betel vine cultivation is a very typical type of farming. For betel cultivation, the best choices are highlands and especially fertile sandy or sandy clay or sandy loam soil with a well drainage system and a pH range of 5.6-8. of planting, the leaves of the plant turn out to be ready for plucking, and the production of betel leaf from the barouj lasts for more than a few years from the time of planting. 41,43,46

| ECONOMIC S TATUS
In the Indian climate, the female plants of Piper betle rarely produce flowers or fruit. Betel vines are cultivated and harvested mainly for their heart-shaped green leaves. 41 This crop has a vast economic potentiality which can be effectively recognized by the piece of F I G U R E 2 Geographical distribution of Piper betle L. throughout the world evidence that more or less 15-20 million of people in India have the habit of using betel leaves regularly 47 not only that, there are more than 2 billion people from many other countries who are recognized as regular users of betel leaves from all over the world. 48 Most importantly, the economic status of betel leaves is dependent on the physical character of the end products in the worldwide market. The betel leaf and products produced in different forms such as powder, capsules, liquid and various types of value-added products are available on a broad spectrum in the market as beverages, in oral care, pharmaceutical products and cosmetics. 41 The annual turnover national income is Rs 7000-10,000 million, and from this, the state, West Bengal, gains an income of 800-1000 million rupees per year.
The leaves were exported to various countries around the world where the plant is not grown naturally or the local supply could not meet the requirements. Betel leaves are generally exported to Hong Kong, Pakistan, Italy, Bahrain, Canada, Great Britain, Kuwait, Saudi Arab, Nepal and several other countries in Europe. 47,49

| TR ADITIONAL AND E THNO -MEDICINAL US E
Traditional medicine has played a crucial role in the health care of the rural and urban people. [246][247][248] Ethno-medico-botanicals have been used across almost all the cultures worldwide against an array of human medical conditions. [50][51][52][53] The use of betel leaf alone and with a combination of other plants or medicines for better therapeutic effects is mentioned in the Ayurvedic literature, which was almost 1400 BC ago. 54 Atharved, the ancient Vedic literature, mentioned the usefulness of the betel plant against numerous diseases at about 3000-2500 BC before. 55 Saptasira, the Vedic name of the leaves of betel, is mentioned in the Kamasutra of Vatsyayan as having aphrodisiac properties. 44 In the ayurvedic and Unani system of medicine, the betel plant is used as an anthelmintic, appetite stimulant, vermifuge, astringent, diarrhoea, aphrodisiac, breath freshener, carminative, cardiac tonic, dentifrice, in the prevention of diuretic emmenagogues, induction and increase of menstrual flow, laxative, strengthen gums, nerve tonic and also in the treatment of urinary disorders. Betel leaves are mostly chewed by about 200 million people on a regular basis throughout the south Asia and western part of the Pacific basin in a special shape of packets known as 'Betel quid', which is prepared from Piper betle leaves brushed with burnt lime and contain few pieces of areca nut, flavours, often cardamom or cloves, are added with or without tobacco according to choice. 56 Chaveerach et al. stated that the betel leaf is a most important material in Thai ceremonies. Elderly people chew betel leaves to prepare quid. In weddings, the family members of the bridegroom place money along with the betle leaves in a bowl, which together is known as khun maak. The ethnic group Kui, from the southern division of North East Thailand, uses betel leaf (locally, raam phi taan) in the 'Spirit dancing' ceremony to chase away evil spirits or fend off bad luck from the patients from the family or the village. They use betel leaves as stimulant, exhilarant, antiseptic and antioxidant, to treat kidney inflammation and thirst resulting from diabetes, strength to stomach, as expectorant for asthma, coughs and bronchitis, and antiflatulent element. 34 Decoction of P. betle leaves used to prevent body odour and treat diarrhoea, sore throat, skin allergies and fluor albus, leaves are cooked and added to vegetable soup. 57 In Southeast Asia, Betel chewing with its associated discoloration of the teeth is the ascriptions of the teeth blackening practice related to sexual maturation and becoming a full member of society in Masticans. 58 In the Laleng community, people use betel leaf to chew and at the sociocultural festival. They oil the leaf with mustard oil and place it on the naval area to relieve liver pain. 59 The Rabha community of Mataikhar forest, Assam, the Torajanese, the Bugis community and Lakshadweep people also use betel leaf for chewing and in religious festivals. [60][61][62][63] People in Parsa district, Nepal, chew betel leaf or mix leaf juice with hot water, honey or milk mild stimulant, cure worm, remedy for bad breath and provides mouth refreshment, improve digestion, strengthen teeth and gums, palate cleaner, treatment of nervous pains and exhaustion, ease of urination, analgesic, reduce cough and cold. 64 The ethno-medicinal uses of P. betle in the area and community are listed in Table 1.

| PHY TO CHEMI C AL PROFILE
Piper betle is one of the extensively investigated plants for its various phytochemical constituents present in it, and the study revealed that the plant contains a wide range of phytochemicals that are biologically active. Compound concentrations depend on the different varieties of the plant, season, climate and may geographical location and also might be influenced by various factors such as soil, humidity, agronomic practices, rainfall, season and type of plant. 65 The main phytochemical constituents of the essential oil of the betel leaf are mainly phenols and terpenes. 66 The phenol content varies by gender, total phenols are three times higher in male plants, and the thiocyanate content is two times higher compared to female plans. Leaf quality is basically dependent on the phenol content; more phenol content comes with better leaf quality. 67 The typical pungent aroma of the betel leaves is the result of the phenols present in them. Preliminary photochemical studies of aqueous and methanol extracts of betel leaves revealed the presence of alkaloids, flavonoids, tannins, sterols, phenols, glycosides, saponins and terpenoids. 68 Syahidah et al. also identified alkaloids, phenols, flavonoids, saponins, steroids, tannins, terpenoids and glycosides from qualitative analysis of the methanolic extract of the betel leaves. 175 Leaves also contain bitter compounds (0.7-2.6%). 2  are also reported as the main elements of the essential oil of the P. betle leaf from Sri Lanka. 67 The leaves were also found to produce an alkaloid, namely arakene, which possesses properties similar to those of cocaine. The chemical compositions of essential oil differ in different parts: leaf, stem, stalk and root contain safrole, while fruits contain β -phellandrene. Younger leaves of betel contain more amount of essential oil. 73  Leaf aqueous extract of varieties bangla, bagerhati, manikdanga, meetha, kalibangla, chhaanchi, ghanagete and haldi GC/MS amino acids: l-glutamic acid (dehydrated), l-pyroglutamic acid, l-tryptophan, organic acids: citric acid, 3,4-dihydroxyphenylacetic acid, fumaric acid, gluconic acid, gluconic acid lactone, glyceric acid, glycolic acid, 3-hydroxy-3-methylglutaric acid, 4-hydroxyphenylacetic acid, isocitric acid, l-(+) lactic acid, maleic acid, malic acid, malonic acid, nicotinic acid, oxalic acid, 3-phenyllactic acid, ribonic acid-gamma-lactone, succinic acid,   Table 2 represents the phytochemical constituents of P. betle. Figure 3 represents the chemical structures of some phytochemicals reported from the species.

| PHARMACOLOG IC AL AC TIVITIE S
The following section summarizes the various pharmacological attributes of P. betle ( Table 3).  The first report of antitumour activity of P. betle came from Rao.

| Antitumour/anticancer/ antiproliferative activity
He studied the activity of the aqueous extract prepared from leaves in benzo(a)pyrene-induced tumours in buccal pouches of hamsters.
The result revealed that the betel leaf extract was very effective in inhibiting preneoplastic and neoplastic changes; partial and complete tumour suppression was also observed in both short-term (10 days) and long-term (6 months) treatment. 90  ing that betel can be used to develop a potential chemopreventive agent for human oral cancer. 94 In another experiment, Bhide et al.
showed that the incidence of virus-induced and 7-12-dimethylbenz (a) anthracene-induced rodent mammary gland tumours can be reduced by 75% and tumour burden by >90% by the administration of the ethanol extract of the leaves. 95 The methanol extract prepared from the leaves was able to exhibit antitumour activity in terms of cancer chemoprevention in Raji cells induced by 12-O-hexadecan oylphorbol-13-acetate. 96 The aqueous extract of leaves and the  Five varieties among the nine varieties showed significant antiinflammatory activity. 116 Another experiment was carried out in which leaf essential oil was used to evaluate the anti-inflammatory activity of P. betle using the detection of MMP-2 (metalloproteinase-2) and MMP-9 (metalloproteinase-9) using the gelatin zymography method in vitro. An effective anti-inflammatory activity with 85% inhibition was observed.

| Nootropic effect
The hydroalcoholic extract of P. betle leaves was shown to have nootropic effect by the experiment in which the extract was administered to Swiss albino mice and the result showed an increase in discrimination index in the object recognition test. 128 In another experiment, the nootropic effect of P. betle in scopolamine-induced amnesia in albino rats was evaluated using the Y-maze test and it was found that the aqueous extract of leaves can reverse the effect against amnesia with a significant decrease in retention latency, a major decrease in the inflection ratio. 129

| Antioxidant activity
Formation of reactive oxygen species (ROS) is one of the major markers in any disease pathology. An antioxidant acts as a protective barrier against ROS, which causes chronic and degenerative diseases. 130 The main health problems such as cancer, cardiovascular diseases, rheumatoid arthritis, Alzheimer's disease and other neurodegenerative disorders may be caused by the formation of free radicals. Antioxidants are very beneficial because they scavenge these free radicals and help prevent these kinds of disorders because they reduce the oxidative injury of cell proteins, carbohydrates and lipids. 131 The extract of the inflorescence of P. betle was found to scavenge free radical (H 2 O 2 , superoxide, hydroxyl radical) with a 50% inhibitory concentration using an in vitro assay.

| ANTIMI CROB IAL AC TIVITIE S
The following section presents the antibacterial and antifungal properties of the plant (Table 4).

| Antibacterial activity
The

| Anthelmintic property
Helminths produce substances, which have substantial toxicity towards humans, that are found in foods acquired from livestock, causing a serious hazard to human health, including lymphatic filariasis or elephantiasis, onchocerciasis, and schistosomiasis. The   204 and cell cycle arrest in the sub-G 0 /G 1 phase. 197 Antileishmanial activity was also reported in which the use of leaf ethanol extract and root extract inhibited promastigotes and amastigotes of Leishmania donovani. 198,199 Inhibition of promastigotes and amastigotes, acceleration in apoptosis, and ROS generation targeting Leishmania mitochondria was also observed using methanol extract of betel leaves of Bangla Mahoba variety. 200 Plasmodium berghei, the causal agent for human malaria, is parasitic protozoa of mosquito. The betel leaf extract showed notable schizonticidal activity (p < 0.05) and an antiplasmodial effect at a dose of 50-400 mg/kg in ICR mice. 201

| Antifilarial activity
In vivoantifilarial activity of P. betle was evaluated using crude methanolic extract, chloroform, and n-hexane extracts were administered at different doses to Balb/c mice. All extracts showed antigen-specific immune response, increased antifilarial IgG antibody and also suppressed microfilaraemia, showed potential macrofilaricidal efficacy, and induced sterilization of female worms. 204

| Insecticidal activities
The insecticidal activity of P. betle was evaluated using an aged grain assay against bean weevil (Sitophilus zeamais), lesser grain borer (Rhyzopertha dominica) and cowpea weevil cowpea weevil (Callosobruchus maculatus). The 30% volatile oil dust formulation exhibited toxicity against adult insects, prevented the survival of adult C. maculatus, and up to 52% protected corn against S. zeamais and R. dominica; also inhibited living and emerging progeny. 205 Nair and Kavrekar found that the methanol extract of betel leaves can exhibit good insecticidal activity against insects such as Bruchus pisorum, Tribolium castaneum and Sitophilus oryzae. 206 The following section presents the insecticidal activities of P. betle ( Table 6).

| Larvicidal property
The mosquito larvicidal activity of P. betle against Aedes aegypti was evaluated using methanol extract and essential oil of the leaves. For essential oil, the LD 50 values were found to be 86 207 The essential oil of the betel leaves can also inhibit the larval growth of Aedes aegypti. When the third instar larvae were exposed for 24 h, the LC 50 value found l3, l ppm, and for the 48-h exposure, the LC 50 value is 1l, 2 ppm. 208 Essential oil from obtained betel leaf was also treated on Chrysomya bezziana larvae, and the result showed that 4% essential oil killed all first instar larvae in 2 h while killing the second instar larvae in 4 h. 209 Larvicidal activity using P. betle essential oil was also observed with LC 50  (TXB2), induced by >90%, indicating that the extract of P. betle contains compounds that can inhibit platelet aggregation by ROS elimination or inhibition of TXB2 production ( Table 3). 213

| Anti-halitosis activity
Halitosis is the degradation of proteins and amino acids present in saliva, gingival cervical fluid or food retained in the teeth that causes bad breath or oral malodour due to microbial activity. The methanol extract and fractions of leaves (isolated compound allylpyrocatechol-APC) showed antibacterial activity against oral bacteria and reduced the production of volatile sulphur compound (VSC) by oral anaerobic bacteria using an in vitro saliva chip model.
APC also potentially reduced methyl mercaptan and hydrogen sulphide and prevented periodontal infection. 214

| Antiallergic activity
To know about the antiallergic activity of the ethanol extract of

| Anti-asthmatic activity
The anti-asthmatic activity of P. betle against 0.2% histamineinduced bronchospasm in guinea pigs was evaluated using ethanol extract. Treatment of the extract, with a dose of 100 and 200 mg/kg bw, exhibited a prominent anti-asthmatic effect with a prolonged latent period of convulsions compared to the standard antihistaminic drug, chlorpheniramine. 216   the main agents responsible for the reduction of n Ag+ions into metallic Ag 0 and also for stabilizing and capping. The morphology and crystalline phase were characterized by selected area electron diffraction (SAED) and transmission electron microscopy (TEM). 226,227 .

| Role in thyroid function
Green synthesis of silver nanoparticles from betel leaf extract was also confirmed and characterized by energy-dispersive X-ray analysis (EDX), X-ray diffraction (XRD), scanning electron micrograph (SEM) and Fourier transform infrared (FTIR) studies. 228 The ethanolic leaf extract of P. betle was also used for the successful synthesis of AuNPs (gold nanoparticles), which were characterized by TEM, Fourier transform infrared (FT-IR), EDX and XRD. These nanoparticles were tested non-toxic to MCF-7 and HeLa (cancer) cell lines. 229 Gadolinium-doped titanium dioxide nanoparticles (GdT NPs) were also synthesized from the leaf of P. betle using the hydrothermal method. GdT NP showed high antibacterial activity against S. aureus, E. coli and C. albicans at 25µg/ml and also showed promising antioxidant activity in the DPPH radical scavenging method. 230 The extract of the leaf of P. betle was also used in the synthesis of titanium dioxide nanoparticles (TiO 2 NP). TiO 2 nanoparticles were characterized by TEM, XRD and FTIR, and antioxidant activity was evaluated using the DPPH assay, which showed promising antioxidant activity with the lowest IC 50 value. 231 The leaf of P. betle helps and techniques for staining with orange acridine or ethidium bromide, also showed no toxicity against non-cancerous human peripheral blood lymphocytes. 236 Another experiment showed that silver nanoparticles synthesized using P. betle showed antifungal potency against Fusarium solani and Alternaria brassicae in a dose-dependent method. 237,238 The Betel leaf extract was used to synthesize a silver-

| CON CLUS I ON S AND FUTURE PROS PEC TS
Piper betle is a world-known herbal cash crop of tremendous, social, economic and therapeutic importance and known as 'green gold'.
The mention of betel leaf is found in various ancient medicinal literatures, and the plant is still used in traditional and folklore medicinal systems. Traditional knowledge and preclinical studies revealed the use of P. betle which has potential multitherapeutic efficacy in various diseases such as cancer, inflammation, neurodegenerative disorders, asthma, dental and oral infections, allergy, thyroid, diabetes and skin diseases. Essential oils and extracts showed great results in antifertility, cardioprotection, hepatoprotection and antiplatelet.
Various researchers have reported remarkable inhibition efficacy against insects, larvae, and improvement in microbial infections, parasitic infections. The plant contains a treasure of bioactive phytochemicals belonging to different classes such as phenol, tannin, terpenoid, alkaloids and flavonoids, which are responsible for healing of various diseases. The beautiful and pungent aroma of the plant is due to its phenolic and terpenoid compounds, which made betel an eminent flavouring agent. In addition to that, betel has a notably nutritional value and is considered GRAS (generally recognized as safe) for consumption.
Piper betle is found in many varieties and cultivars, and there is a problem in synonym and proper authentication; therefore, proper taxonomic identification of landraces is the most important criterion in research. Genetic and molecular markers must be used to differentiate the different varieties of betel. Different landraces contain different amounts and combinations of chemical constituents; therefore, efforts must be made to identify phytochemicals using modern extraction and detection techniques. Standardization and validation of chemical constituents for quantitative and qualitative evaluations must also be taken care of. As the quality and quantity of the chemical constituents vary with soil and environmental factors, therefore, the optimization of the highest-yielding soil quality and factor must be studied for large-scale commercial cultivation purposes. Although there are many reports available on preclinical treatment using P. betle in various diseases, the mechanism of the reaction is not mentioned in most reports. A computer-aided drug discovery program can be used since it clarifies the molecular mechanisms, correlates the pharmacological responses with experimental data, and has a crucial role in boosting medical and pharmaceutical innovation. The docking analysis performed in this research provided valuable insights into the bindings of bioactive isolates towards many protein targets, including those involved in antidepressant, anti-inflammatory and thrombolytic cascades. 237,238 Broad-spectrum clinical studies are also a major lacuna, which is incomplete in the pharmacological study. Therefore, more attention must be paid to the mechanism of action in different disease man-

CO N FLI C T O F I NTE R E S T
The authors declare that there are no conflicts of interest. Data curation (supporting); writing, review, editing (supporting).

DATA AVA I L A B I L I T Y S TAT E M E N T
Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.