Science of Spices & Culinary Herbs: Volume 5

Clove: The Spice of Polyvalent Merit

Abdul Jalil Shah¹, Reyaz Hassan Mir¹, *, Roohi Mohi-ud-din², Prince Ahad Mir³, Saba Sabreen¹, Rafia Jan⁴, Taha Umair Wani⁵, Shah Asma Farooq⁶, Mubashir Hussain Masoodi¹, *

¹ Pharmaceutical Chemistry Division, Department of Pharmaceutical Sciences, School of Applied Sciences and Technology, University of Kashmir, Hazratbal, Srinagar-190006, Kashmir, India

² Pharmacognosy and Phytochemistry Division, Department of Pharmaceutical Sciences, School of Applied Sciences and Technology, University of Kashmir, Hazratbal, Srinagar-190006, Kashmir India

³ Amritsar Pharmacy College, 12 KM Stone Amritsar, Jalandhar GT Road, Mandwala-143001, India

⁴ Department of Pharmacology & Toxicology, National Institute of Pharmaceutical Education & Research (NIPER), Mohali, Punjab-160062, India

⁵ Department of Nanotechnology, University of Kashmir, Hazratbal, Srinagar-190006, Kashmir, India

⁶ MM College of Pharmacy, Maharishi Markandeshwer Deemed to be University, Mullana, Ambala, India

Abstract

Syzygium aromaticum (Family Myrtaceae), commonly acknowledged as clove, is one of the most valuable spices in the world trade market with global distribution, though Indonesia has maintained its top position as a producer. Clove has sustained its value in the past, dating back to 1700 BC, as is evident from clove found in a ceramic vessel in Syria and modern society. It is well integrated into culinary and non-culinary practices. Apart from culinary use, its distinctive chemical style has demonstrated incredible potential for cosmetic, medicinal, nutrition, and agricultural applications. The ORAC (Oxygen Radical Absorption Capacity) of the clove is above 10 million, making it the most potent antioxidant source ever found in a natural system. Clove imparts a vast range of activities due to various chemical compounds, for example, phenolics, monoterpenes, sesquiterpenes, and other hydrocarbon compounds. The significant phytoconstituents present in clove oil are primarily eugenol (70-85%), trailed by eugenol acetate (14-15%), and β-caryophyllene (5–12%). Their derivatives result in an extensive gamut of biological activity as antifungal, herbicidal, nematicidal, antitumor, anti-inflammatory, antioxidant, antiviral, antimicrobial, antidiabetic, antithrombotic, anaesthetic, pain-relieving, and insect repellent properties. Clove also finds its exceptional locus among various traditional medicinal practices.

Along these lines, it is wise to say that clove itself has magnanimous pride among natural products. That is why we thought of covering its phytochemistry, phytopharmacology, and traditional values in detail. This chapter aims to present a comprehensive review of traditional and ethnomedicinal uses of clove in traditional medicine. We will then discuss the pharmacological activities reported for clove.

Keywords: Antioxidant, Clove, Eugenol, Pharmacological properties, Phytochemistry, Traditional medicine.

* Corresponding authors Mubashir Hussain Masoodi and Reyaz Hassan Mir: Department of Pharmaceutical Sciences, School of Applied Sciences and Technology, University of Kashmir, Hazratbal, Srinagar-190006, Kashmir, India; Tel: 9419076525; E-mail: [email protected] and

E-mail: [email protected], respectively

INTRODUCTION

Syzygium aromaticum (Clove) is a dried, aromatic, and unopened flower bud obtained from a tree belonging to the Myrtaceae family, a taxon of dicotyledon plants [1]. Syzygium is the largest genus of the Myrtaceae family, comprising about 1200 to 1800 species of flowering plants. Various synonyms used for the clove are Caryophyllus aromaticus, Caryophyllus silvestris, Eugenia caryophyllus, Jambosa caryophyllus, and Myrtus caryophyllus [2]. Clove is known by different vernacular names in different languages. It is known as qaranful (Arabic), Karamfil (Bulgarian), Ding Xiang (Chinese), Jeonghyang (Korean), Kruidnagel (Danish), Garifalo (Greek), Gvosdika (Russian), Clavo (Spanish), Mikhaki (Georgian), Nelke (German), Szegfu (Hungarian), Cengkeh (Indonesian), Choji (Japanese), Krustnaglinas (Latvian), Laung (Urdu/Punjabi/Hindi) Lawang (Nepalese), Carvo de India (Portuguese), Mikhak (Persian), Carenfil (Turkish), Garn ploo (Thai), Dhing Huong (Vietnamese), and Kala (Pashto) [3]. Clove is found in tropical and subtropical areas of Asia, Africa, Madagascar, and throughout Pacific and Oceanic regions [1, 2]. Clove is the most essential and second valuable spice in world trade and is widely cultivated in North Maluku Islands in Indonesia. Major cultivator countries of clove are Pemba, Zanzibar, Indonesia, Madagascar, and some wild clove varieties found in Bacan, Ternate, Motir, Tidore, Makian, and Western parts of Irian Jaya [4].

BOTANY, TAXONOMY & DISTRIBUTION

S. aromaticum is an evergreen tree that grows up to a height of 8-12 m; branches are semi-erect, greyish in color, and dense. Leaves are large oblong to elliptic, simple obovate opposite, glabrous, and possess plenty of oil glands on the lower surface. The tree begins flowering in about seven years and continues flowering for 80 years or more [4]. Flowers are small, crimson in color, and hermaphrodite (bisexual) borne at the terminal ends of short branches arranged in clusters. Each peduncle carries 3 to 4 stalked flowers, and inflorescence length remains between 4 to 5 cm (Fig. 1). Young flower buds are pale in color and slowly change to green and further to bright red when buds are ready for harvesting. These are 1-2 cm long with a thick cylindrical ovary consisting of four fleshy sepals. Buds are divided into an elongated stem and a globose bulbous head, which stimulates the nail. Fruit matures nine months after flowering, and the red ovary gradually turns to reddish-purple. The fruit nearly contains one or two seeds known as the mother of clove. The cultivated trees are rarely allowed to reach the fruit stage. These are harvested when they develop dark red ellipsoid berry. Harvesting should be done when buds have 1.5–2 cm length, long calyx terminating in four closed petals (forming a tiny ball in the core) and spreading sepals [3, 5, 6]. Clove growth requires well-drained, loamy, and organic matter-rich soils. Constant temperature above 10 ºC is crucial, while the optimum temperature is around 20 to 30 ºC. Clove tree requires heavy sunlight with high atmospheric temperature (25 to 35 °C), well-distributed rainfall 150 to 300 cm, and high humidity above 70% [7]. This species cannot tolerate soggy conditions [3]. S. aromaticum (L.) tree is habitually grown at 200 m altitude above sea level in coastal areas. Clove buds are collected before flowering during the maturation phase. The collection is done either manually or chemically using a natural phyto-hormone that releases ethylene in the vegetal tissue, producing precocious maturation [9].

Fig. (1))

S. aromaticum aerial parts.

Taxonomical classification of S. aromaticum (L.) [5]:

Kingdom: Plantae

Subkingdom: Tracheobionta

Superdivision: Spermatophyta

Division: Magnoliophyta

Class: Magnoliopsida

Subclass: Rosidae

Order: Myrtales

Family: Myrtaceae

Genus: Syzygium

Species: aromaticum (L.)

ETHNOMEDICINAL/TRADITIONAL USES

Clove has been used as a spice in food cuisines worldwide since time immemorial. It has also been used in the treatment of various infections [8, 9]. In traditional medicine, the clove buds are used as an aromatic condiment, diuretic, carminative, tonic for cardiac muscles, stomachic, and as stimulant [10]. In the Indian and Chinese traditional system of medicine, cloves have been used as a warming and stimulating agent [11]. In the traditional medicines of Australia and Asian countries, clove has been a popular remedy for headache, sore throat, dental and respiratory disorders, digestive system ailments [12]. It has also been used as an expectorant [13]. In Tropical Asia, cloves were used to treat several infections like malaria, tuberculosis, scabies, and cholera. In America, cloves were traditionally used to treat worms, candida, viruses, various protozoan and bacterial infections [13]. It has also been reported to be traditionally used as an antimicrobial agent [14, 15]. S. aromaticum has been used as a carminative to improve peristalsis and to increase hydrochloric acid in the stomach [16]. Traditionally, cloves have been used to treat flatulence, nausea, and vomiting [17]. Cloves are a natural anthelmintic [18, 19]. They have also been used to promote the flow of gastric juices and saliva. Cloves were, for over the centuries, used as a drug for the treatment of most liver, stomach and bowel ailments, diarrhoea, and as a nerve stimulant [13]. S. aromaticum finds its use in Ayurvedic, Chinese, Western medicine, and dentistry [20]. Clove is an anodyne for dental emergencies [21]. Clove can be used to relieve toothache by applying to the cavity of a decayed tooth as well as can be used as an antiseptic [22]. S. aromaticum has been used for over 2,000 years, in India and China, as a spice, as well as a treatment for both tooth decay and counters lousy breath, throat and mouth inflammation [13]. In folk medicine, leaf oil of clove has also been used for the treatment of burns and cuts [23]. In the Ayurvedic system of medicine, the clove has been used to treat male sexual disorders because of its aphrodisiac property [24].

Methods

We searched Google Scholar, Science Direct, and PubMed, using the following terms; S. aromaticum ethnomedicinal/traditional uses, phytochemistry, pharmacological, clove activities etc. The information was gathered from all applicable scientific literature.

PHYTOCHEMISTRY OF CLOVE

Clove has been investigated for its chemical constituents by various researchers and has been reported as the main source of phenolic molecules like flavonoids, hydroxycinamic acids, hydroxybenzoic acids, hydroxyphenyl propens, and gallic acid that are found in high amounts in the fresh plant [6, 21, 25-27]. The clove buds mainly comprise 15-20% of volatile oil with eugenol, eugenol acetate and β- caryophyllene being the major compounds and making nine-tenth of the volatile oil. The other essential constituents being vanillin, crategolic acid, methyl salicylate, eugenin, kaempferol, rhamnetin, eugenetin, α and β humulene, and chavicol. The characteristic odour of cloves is attributed to methyl amyl ketones and methyl salicylate. In addition to these sesquiterpenes like α-cubebene, α-copaene, γ and δ cardinene have also been reported in clove essential oil [28]. Indian clove bud oil comprises approximately 13-19% of volatile oil, with half of it being eugenol [3]. On categorizing, the researchers have observed that as phenolics, the constituents are eugenol, hydroxybenzoic acid, flavonoids, hydroxyphenyl propens, hydroxylcinnamic acids, ferulic acids, ellagic acids, caffeic acids, salicylic acids and hydrolyzable tannins. Also, kaempferol and quercetin present in clove essential oil belong to flavonoid class [6, 29]. In addition to normally reported compounds, Alma et al. have reported the presence of chavibetal, trisiloxanel, 1, 1, 5, 5, 5-hexamethyl-3, 3-bis [(trimethylsilyl) oxy], etc. in the clove essential oil [4, 30]. Also, another study reported the existence of novel constituents like caryophyllene oxide, α-selinene, and 2-pinene by GC-MS analysis of clove oil [31]. 3-Phenyl prop-2-enal was reported as another constituent in addition to normally present compounds in a study [32]. The compounds are enlisted in Fig. (2).

PHARMACOLOGICAL ACTIVITIES

Natural products are receiving tremendous attention worldwide in the management of different health issues [33-39]. Natural products from various sources, including plants, animals, marine, and minerals, are a repository of potential leads and are explored by researchers to treat different diseases [40-43]. S. aromaticum has been considered worldwide as an essential medicinal herb and exhibits therapeutic activities including anti-inflammatory, antioxidant, antimicrobial, anaesthetic analgesic, and anticancer effects and is found to be comparatively safe (Table 1).

Fig. (2))

Chemical constituent of S. aromaticum.

(1) Eugenol (2) Eugenol acetate (3) β-Caryophyllene (4) Vanillin (5) Crategolic acid (6) Methyl salicylate (7) Eugenin (8) Kaempferol (9) Rhamnetin (10) Eugenetin (11) α-Humulene (12) β-Humulene (13) Chavicol (14) Methyl amyl ketone (15) α-Cubebene (16) α-Copaene (17) γ-Cardinene (18) Hydroxybenzoic acid (19) Hydroxyphenyl propen (20) Hydroxycinnamic acid (21) Ferulic acid (22) Ellagic acid (23) Caffeic acid (24) Salicylic acid (25) Chavibetal (26) Caryophyllene oxide (27) α-Selinene (28) 2-Pinene (29) 3-Phenylprop-2-enal.

Antioxidant Activity

The research was conducted to assess the antioxidant potential of clove oil. The study results revealed that the essential oil possesses prominent DPPH scavenging potency with little effect on hydroxyl radicals. The hexane extract was evaluated for antioxidant activity of isolated volatile compounds from Syzygium aromaticum and demonstrated that 16 volatile compounds were isolated from various clove extracts, among which eugenol (71.56%) and eugenol acetate (8.99%) were major compounds. All the extracts and isolated compounds showed prominent DPPH scavenging activity. Alcoholic extract of Syzygium aromaticum possesses prominent radical scavenging activity in DPPH, superoxide hydroxyl, H2O2, metal chelating and nitric oxide models with IC50 values 95, 101, 250, 225, 78, and 215 μg/mL, respectively. The extract prominently blocks lipid peroxidation by 88% at 1mg/ml concentration [44]. In a study, to authenticate the scavenging potency of essential oil and various extracts viz. hexane, ethyl acetate, and aqueous obtained from clove buds. The results revealed that the essential oil possesses prominent scavenging properties followed by ethanol and hexane extract. The scavenging property of essential oil was found due to its active constituents like eugenol, β-Caryophyllene, eugenol acetate, and α-Humulen [45].

Anesthetic Activity

The research was conducted to authenticate the local anesthetic potency of β-caryophyllene, an essential constituent of the oil isolated from S. aromaticum, using in-vivo and in-vitro models. β-Caryophyllene (10-41 μg/mL) was capable of decreasing the shrinking of rat phrenic nerve compared to caryophyllene oxide. In rabbit, conjunctival reflex test, β-caryophyllene prominently elevates stimuli number, which is essential to provoke reflex [46]. Anesthetic and analgesic potency of water extract of S. aromaticum was evaluated on human α1β2-GABAA receptor using a di-electrode voltage-clamp procedure. The extract prominently and precisely enhances GABA-produced currents by allosteric regulation (0.5–5 µg/mL up to 426 ± 23%). Activity-guided, HPLC bifurcation showed eugenol the element for GABAergic potency. Thus, it was found that eugenol is responsible for the analgesic potency of clove, which modulates the GABAA receptor partially [47]. The research was conducted to authenticate anaesthetic, recovery, and muscle relaxant potency of clove oil on banded cichlid, cardinal tetra, Amazon freshwater fish species, and angelfish. The results demonstrate that clove essential oil encourages deep anaesthesia (<3 min) in cardinal tetra and angelfish at a concentration of 90 μL/L, whereas in banded cichlid anaesthesia was produced at a concentration of 60 μL/L [48]. The study was carried to evaluate silkworm's muscle contraction (Bombyx mori) in the presence of S. aromaticum oil and eugenol individually. Results revealed that both S. aromaticum oil and eugenol at 60 ppm produce anaesthesia in fishes at stage 4 compared to D-glutamic acid, which showed total equilibrium loss and muscle tone in fish stage 4 [49]. Eugenol obtained from S. aromaticum oil was evaluated for anesthetic potency on larva and juvenile of Oreochromis niloticus (Nile tilapia). The results revealed that eugenol possesses a prominent analgesic effect at a concentration of 150 and 175 mg/L on larva weighing (11.64 g) [50].

Anti-bacterial Activity

The research was carried to authenticate the anti-bacterial potency of ethanolic and methanolic extracts of clove towards foodborne pathogens. The data obtained revealed that methanol extract possesses prominent anti-bacterial activity in both gram-negative and gram-positive cultures in comparison to ethanolic extract, research was conducted [51]. Water extract of S. aromaticum seeds was evaluated for bactericidal potency towards E. coli, P. aeruginosa and S. aureus. GC was used to determine the content of various Phytoconstituents available in the extract. The extract revealed prominent antimicrobial activity with 0.06 mg/mL MIC and 0.10 mg/mL MBC respectively. Extract prominently reduces density and colony formation potency of E coli, P aeruginosa and S. aureus. Superoxide anion radical, superoxide dismutase and catalase activities, glutathione, and malondialdehyde in bacterial cells were prominently elevated following extract exposure. From these results, it was concluded that water extract of clove prominently increases membrane permeability and oxidative stress in tested strains [52]. Anti-bacterial potency of eugenol isolated from S. aromaticum leaf essential oil and its mechanism were evaluated against oral anaerobe Porphyromonas gingivalis. Electron scanning microscope was used to determine cell shrinking and cell lysis due to eugenol. The data obtained showed that eugenol content (90.84%) in leaf essential oil possesses prominent bactericidal potency towards P. gingivalis at a dose of 31.25 μg. Macromolecules discharge and fluorescent dye uptake revealed that antibacterial potency was due to increased cell permeability and irreversible plasmatic membrane destruction [53]. The research was conducted to authenticate the antibacterial potency of water and alcoholic extract of Syzygium aromaticum whole bud using the disc diffusion method. The results revealed that the alcoholic extract prominently inhibits microbial load as compared to water extract. The alcoholic extract showed 17 to 23 mm of minimum inhibitory concentration compared to water extract, i.e., 12 to 16 mm [54]. Syzygium aromaticum oil showed prominent bactericidal potency towards tested microorganisms with 30 to 50 μl/L for MIC and 60 to 120 μl/L for MBC, respectively [55]. The research was proposed to authenticate antibacterial and leishmanicidal potency of oil and eugenol isolated from Syzygium aromaticum. The results revealed that essential oil (EO) extracted from clove possesses non-significant antimicrobial potency towards S. aureus, E. coli, P. aeruginosa, and K. pneumoniae, as compared with eugenol. Both EO and eugenol possess pronounced leishmanicidal effects against Leishmania tropica and Leishmania major. It was concluded that both essential oil and eugenol possess main antibacterial and leishmanicidal activities. However, EO is preferable to eugenol due to its lower cost [56].

Antifungal Activity

The research was conducted to authenticate the antifungal property of S. aromaticum oil towards Aspergillus sp., Microsporum gypseum, Fusarium oxysporum MTCC 284, Mucor sp., Fusarium moniliforme NCIM 1100, and Trichophyton rubrum using agar well diffusion technique. The data obtained demonstrated that the oil prominently inhibits all tested fungal strains. Microscopic analysis of Mucor sp. and M. gypseum spores revealed shrinking and distortion [57]. Oil isolated from S. aromaticum was claimed to possess mild to potent antifungal potency against infective fungus. Clove oil at the concentration of 1 µL/mL totally blocks the growth of F. oxysporum