3. Phenolic compounds present in Areca nut : Part - I

 

Areca nut contains a large number of phenolic compounds in substantial quantity. Flavonoids (flavones, flavanones, flavanols, flavonols), phenolic acids and polyphenols (procyanidins, areca tannins etc.) are some of the important classes of phenolic compounds found in areca nuts. These compounds are responsible for the dark brownish color in the boiled nuts (Red supari). They impart astringent taste, and they turn red in the presence of lime. Most of the perceived therapeutic properties of areca nut are attributed to these flavonoids, phenolic acids and polyphenols. Almost all of them are highly potent antioxidants. A brief account of proven health benefits of some of the prominent phenolic compounds present in areca nut shall be posted in subsequent Blogs.

Very few reports are available on the systematic study of total phenolic compounds present in the areca nuts at its developmental stages. A brief account of those reports is presented below.

Thailand

Total phenolic content of areca nuts cultivated in Nakhon-Pathom province of Thailand was estimated by Wetwitayaklung et al., (2006).  They have used a standard method to extract and analyze the phenolic content of areca nuts of maturity 1 month to 8 months. They have reported that the total phenolics is in the range of 8 mg/g (by weight on dry basis) in the 1-month-old nut, reaches 10.5 mg/g at the 4th month and reaches 7 mg/g in the 8th month areca nut. The results of their study are presented below. 

Indonesia

One more recent study on the estimation of chemical constituents of areca nuts was reported from Indonesia. Sari et al., (2020) had studied the total phenolic content of unripe (green) areca nuts (6-7 months’ maturity) collected from West Kalimantan and West Papua and ripened areca nuts (perhaps 9-10 months’ maturity), collected from Banda Aceh & North Sumatra, Indonesia. The phenolic content was in the range of 10.88 mg/g to 21.67 mg/g on dry weight basis. The unripe (green) nut collected from West Papua province of Indonesia had the highest phenolic content 21.67mg/g on dry basis, whereas the unripe (green) nuts from West Kalimantan had only 10.8 mg/g of Phenolic compounds. The mature areca fruits from North Sumatra & Banda Aceh had phenolic content of 11.1 mg/g & 12.2 mg/g respectively.

China

A recent study on the total phenolic present in the areca nuts of 5 months maturity has been reported by Song et al., (2022). They had chosen the areca nut samples from Hainan Province of China and they analysed the phenolic content of the seed after separating the husk. They reported the total phenolic content of 36.3 mg/g on dry weight basis. In another study, Wang et al., (2023) had analysed the total phenolic content of areca nut (with husk) of 5 months maturity, collected from 11 prominent areca growing regions of Hainan Province of China. They had used High Performance Liquid Chromatography (HPLC) method to determine the phenolic content. They have reported an average value of 36 mg/g (on dry weight basis). As they had estimated the Phenolic content of areca nut along with the husk, the values seem to be highly inflated.

From the aforesaid literatures, it is clear that there is a great variability in their concentrations in areca nuts cultivated in different regions of the world. The values varied from 6.98 mg/g (8-month sample from Thailand) to 36.3 mg/g (5-month sample from China). The unripe (green) areca nuts of 4 to 5 months maturity have the highest concentration of Phenolic compounds. Interestingly, the areca nut of 4-5 months maturity is harvested and processed to make flavoured Bing lang in China (Refer my Blog No. 6 & 7 under the label “Global areca nut production”).   

References:

1.     1.  Wetwitayaklung et al., (2006). The study of antioxidant capacity in various parts of Areca catechu L. Naresuan University Journal, Vol. 14 (1), pp. 1-14.

2.    2. Sari et al., (2020). Distinct phenolic, alkaloid and antioxidant profile in betel quids from four regions of Indonesia, Scientific Reports, Vol. 10:16254

3.    3. Song et al., (2022). UHPLC-MS/MS identification, quantification of flavonoid compounds from Areca catechu L. extracts and in vitro evaluation of antioxidant and key enzyme inhibition properties involved in hyperglycemia and hypertension. Industrial Crops & Products. Vol. 189, pp. 115787.

4.   4.Wang et al., (2023). Evaluation of Areca Quality Based on Principal Component and Hierarchical Cluster Analyses in Hainan, China. HORTSCIENCE, Vol. 58(6), pp. 699–703.

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2. Major constituents of Areca nut (Supari)

The major constituents of the areca nut are carbohydrates, lipids, proteins, crude fiber, phenolic compounds (flavonoids, phenolic acids and polyphenols), alkaloids and mineral matter. Jayalakshmi & Mathew (1982) have reported that the unripe areca nut of 6-7 months’ maturity will generally have a moisture content in the range of 69.4–74.1% (by weight) whereas the ripe fruit will have moisture content in the range of 38.9–56.7 %. The moisture content will vary depending upon the variety, agroclimatic conditions and the agriculture practices.

The major chemical of unripe green (6-7 months’ maturity) and ripe areca nuts are given below on dry weight basis except for moisture (Adapted from Jayalakshmi & Mathew (1982)). Rudimentary analytical techniques and instruments available at that time were utilized to estimate the components. Nevertheless, the following Table gives the rough estimation of major components. 

As per the report of Mathew et al., (1964) from CFTRI Mysore, who had studied the composition of areca nuts harvested at 2 months, 4-5 months, 6-7 months and 9 months’ maturity collected from Kyatsandra, Mysore, Thirthahalli and Vittal in Karnataka state and Pudupady in Kerala, the lipid (oil) content of the areca nut increased from a low, 1-4 %, in the tender stages to a high, 10-15 %, in the ripe stage. Similarly, the polysaccharide (starch and cellulose) content also starts with a low value at the tender stage and increases progressively until at ripe stage. Crude fibre (cellulose and hemicellulose) starts with a very low value (1-2 %) and with maturity and ripening fibre will be formed continuously and the rate of formation increases until the ripe areca nut showed a value of about 15 %. Rapid protein accumulation happens till the fruits are 3 months old and thereafter the value remained more or less constant. Phenolic substances start with a high value in the early stage and progressively decrease during the developmental stage and reaches the lowest value in the fully ripened fruit. The considerable increase in the hardness of the nut coincides with drop in moisture content and build-up of polysaccharides and crude fibre. Lignification (formation of lignin) and high degree of polyphenol polymerization occur in matured fruit, contributing to the larger insoluble residue and increased hardness of the nut. While the trend in changes of physical and chemical properties with maturity for the samples from different regions was the same, individual variations in relative proportion of constituents were significant.

The study by Jayalakshmi & Mathew (1982) and Mathew et al. (1964) clearly demonstrates that the protein content, lipid content and crude fiber content will be highest in the mature fruit (9-10 months maturity) which is used for making Chali (White supari) and Niradike (Doma, fermented Areca nut). Water content in the areca nut keeps decreasing during the developmental stage and reaches the minimum value in the matured fruit compared to its early stages.

Other major constituents such as Phenolic compounds and alkaloids shall be discussed in my subsequent Blogs.

Reference:

1.      Jayalakshmi A, Mathew AG (1982) Chemical composition and processing. In: Bavappa KVA, Nair MK, Kumar TP (eds) The areca nut palm. Central Plantation Corps Research Institute, Kerala, pp 225–244.

2.      Mathew A.G, Venkataramu S.D, Govindarajan V.S (1964). Studies on Arecanut: Part I - Changes in Chemical Composition & Physical Characteristics of Nuts with Maturity. Indian Journal of Technology, Vol. 2, No.3, pp. 90-96.

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1. Chemical constituents of Areca nut

A handful of research papers are available on the composition of areca nut. However, only a couple of papers can be considered for all the practical purposes as they used standard protocols and sophisticated instruments ensuring reproducibility and sensitivity. 

Review of processing practices of areca nut in various major areca growing regions of the world shows that areca nut is harvested at four different stages of maturity.

1.      Unripe areca nut of 2-3 months maturity (In Taiwan and consumed fresh with husk)

2.      Unripe areca nuts of 4-5 months maturity (In China, sliced and smoke dried)

3.      Unripe areca nuts of 6-7 months maturity (In India, Indonesia, boiled and sundried)

4.      Ripe areca fruits of 9-10 months maturity (In India, Bangladesh, Bhutan, Malysia, Thailand, Indonesia etc. sundried or fermented.)

Areca nut is processed in four different ways, after harvesting, as follows.

1.      Unripe areca nuts of 4-5 months maturity: Sliced and smoke dried. Steeped in sugar, mint syrup to impart flavour and dried. Marketed as Bing lang in sachets in China.

2.       Unripe areca nuts of 6-7 months maturity: Boiled in Chogaru/Kali repeatedly and sundried, sold as Red Supari (Kempadike) in India and Indonesia.

3.      Ripe areca fruits of 9-10 months maturity: Dehusked and sun dried, sold as White Supari (Chali) in India, Bangladesh, Bhutan, Malysia, Thailand, Indonesia etc.

4.      Ripe areca fruits of 9-10 months maturity: Fermented under the earth or in water tanks, sold as Niradike or Doma in India (assam, Meghalaya) & Bhutan.

Considering the fact that areca nut is harvested at different stages of maturity and processed by different methods, chemical composition of the final product is bound to change substantially. Hence it is not possible to state a one general composition of areca nut, which is applicable to all the varieties. Furthermore, the agroclimatic conditions also known to influence the composition of the areca nut to a great extent, especially with respect to some of the important active principles. Areca nut of India is found to possess different chemical composition in comparison to areca nut of Indonesia and elsewhere. Unfortunately, the reports on all these varieties are not available. However, I am going to make an effort to present the composition of areca nut in my subsequent posts under the label "Chemical constituents of areca nut". 

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7. Areca nut consumption pattern in South & Southeast Asia: A summary

 

The Asian Betel quid Consortium (ABC) study in 2011 (comprising of Taiwan, China, Malaysia, Indonesia, Nepal, and Sri Lanka) found that the prevalence of betel quid and areca nut chewing in the adult male population varied from 10% in Malaysia to 44% in Nepal; and from 2.3% in mainland China to 47.8% in Indonesia among women. Surprisingly in Malaysia and Indonesia, the use among women was higher (32% and 48%, respectively) than for men (10% and 12%).

There is a great diversity in the way areca nut is consumed in different countries. In most of the country's areca nut is chewed with betel leaf and lime. Tobacco is an important adjunct used in Betel quid in several countries. Flavored areca nut alone is consumed as a mouth freshener in certain countries. There is an increasing trend in area nut consumption in countries like India, Pakistan, Bangladesh, Papua New Guinea and also a sharp decline in areca nut consumption is being witnessed in countries like Thailand and Taiwan. 

In general, the practice of Betel quid (Tambula) chewing among the general public in most of the southeast Asian countries is based on four factors: social acceptability, religious beliefs, perceived health benefits and addiction. In India, Indonesia, Thailand, Myanmar and Cambodia, offering ingredients of Tambula (areca nut and betel leaf) is an integral part of several religious ceremonies. There is a social acceptability, and it is the normal practice to consume Tambula after the feasts and in social gatherings.

In India and Pakistan, Gutkha (areca nut mixed with flavoured tobacco and slaked lime) consumption has become a major addiction. In Taiwan, chewing unripe areca nut with husk of 2-3 months maturity with lime powder and betel vine spike has become an addiction. In Papua New Guinea, chewing dehusked unripe areca nut of 6-7 months maturity with betel vine spike and lime powder is an addiction. 

A summary of areca nut consumption pattern in the major areca nut consuming countries is given below.  

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6. Areca nut consumption pattern in India

 

India is the world leader in Areca nut production. India consumes most of its domestic areca nut produce. Paan (Betel quid, Tambula) made out of areca nut, betel leaf and slaked lime with or without tobacco is chewed in India. Both major variants of areca nuts, such as Chaali (white supari), Kempadike (red supari) are used for making the betel quid. Betel quid made out of areca nut slices / pieces, sweetened rose petals (Gulkand), cardamum, clove, fennel seeds, grated coconut etc. wrapped in betel leaf laced with catechu extract and lime is a popular dessert among the urban consumers. Apart from this, areca nut is also consumed in the form of Paanmasala, Gutkha and Mawa. All the three are dry preparations, wherein Paanmasala and Gutkha are produced by major companies and are packed in attractive sachets. Whereas Mawa is prepared by Paan vendors as per the preferences of the consumer. It essentially consists of tobacco (Zarda, Kiwam etc.) Chaali (or roasted Chali) and slaked lime. Paanmasala is basically a preparation of areca nut (mostly red supari), Catechu extract, cardamom, lime and number of natural and artificial perfuming and flavoring materials. Gutkha is the variant of Paanmasala in which, in addition to ingredients of Paanmasala, flavored chewing tobacco is added. Usually, Paanmasaala is prepared out of red supari (Kempadike) or roasted Chali (also called as Pakka supari). 

As per a nationwide representative cross-sectional study conducted in 2016-17, about 23.9% of the adult population consume areca nut in India. This translates into approximately 22.38 crore people consuming areca nut in one or the other form in 2016-17. Majority users (13.29 crore) consumed areca nut with tobacco. In four states, Meghalaya, Assam, Mizoram and Manipur, over half of the population consume areca nut. Furthermore, Karnataka, Uttar Pradesh, Tamil Nadu, Maharashtra and Odisha constitute nearly 55% of the country’s areca nut users. The age-wise pattern suggests that areca nut consumption without tobacco began to decline from age 51 onwards. But in the case of areca nut consumption with tobacco and in both forms, it increased with age. Higher consumption of areca nut with tobacco & without tobacco was found among daily wage/casual labourers compared to the educated and affluent class. Compared to the Hindus, Muslims were found to consume more betel quid with and without tobacco. Urban–rural differences by state suggest that in 18 states, areca nut consumption was higher in urban areas than in rural areas. Interestingly, consumption of areca nut without tobacco was higher in urban areas than their rural counterparts.

In general, the practice of Tambula (Betel quid, Paan) chewing among the general public is based on four factors.

1. Social acceptability. 
2. Religious beliefs
3. Perceived health benefits
4. Addiction.

In India, due to the historical reasons, Tambula (Betel quid) has a very high level of social acceptability. Majority believes in the health benefits of Tambula due to the higher influence of traditional medicinal systems such as Ayurveda and Unani. None of the Hindu rituals will be complete without offering Tambula to the deity and to the priests. Interestingly tobacco has no place in Hindu rituals. Unlike few countries such as Papua New Ginea and Taiwan, areca nut addiction is not a reason for areca nut consumption in India. However, those who are addicted to the tobacco, consume areca nut in the form of betel quid (Tambula), Gutkha, Mawa. 

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