What about centella as a food ingredient?
Centella is commonly eaten fresh as vegetables (ulam, soup and salad), especially among the locals Malay and Javanese populations [1]. The salads are eaten together with the main meal and can act as an appetizer.
Besides being eaten raw, it can be cooked as a soup or as a main vegetable, notably in Yunnan and Guangxi, Chinese provinces. In China, its mild bitterness is appreciated, but in Southeast Asia, to moderate it, Centella is usually cooked and served with coconut milk and/or shredded coconut and sometimes sweet potatoes.
Centella is used as a health tonic in Malaysia and is processed into cordial drinks and ready to drink juice [2]. The fresh plants are also blended to make a drink and juice.
It is used as a vegetable and tonic in Thailand, drunk as tea and juice [3]. The freshly prepared juice is popular and available in restaurants and is even sold by the roadside. It is commonly used as a drink by the Thai and Chinese people for thirst-quenching purposes or cooling drinks and reducing the “inner heat” to assist in healing and curing of aphthous ulcers |4].
In Sri Lanka, the Centella leaves are used in their traditional curry called “mallung” and their porridge known as “kola kenda”.
In India, it is one of the constituents of the Indian summer drinks “thandaayyee” and is very important for brain tonic.
Inspirations From Nature With A Touch Of Human
Salad
Soupe
Juice
Porridge
Centella is also commonly used for making herbal tea whereby the infusion is made by pouring a cup of boil water over the Centella materials either using dried Centella or fresh materials, letting it brew a few minutes before drinking. The Centella herbal tea can be prepared either using a mixture of many different herbal plants or a single plant. It is believed the Centella herbal tea is considered as source of antioxidant activities and it has many beneficial effects |5] .
It is a common practice to process Centella into many products. These Centella based products are available in many forms such as powder, infusion, soluble and extract of fresh and dried plants. One of the processed products is Centella herbal drink, whereby the demand for this product is on the rise due to its health benefits and the phytochemicals presence [6] .
The essentials oil of Centella could provide an alternative source of synthetic antioxidant BHA.
Antioxidant capacity
The consumption of Centella is useful for the antioxidant effect as it offer an effective and safe way of increasing body immune system against free radicals [7] and at the same time keep the oxidative stress in a state of balance [8] .Some studies have reported that Centella possesses antioxidant properties (84%) and that they are comparable to Vitamin C (88%) and grape seed extract (83%) [9].
Among the triterpenes isolated from Centella plant, asiaticoside is the most abundance and responsible to stimulate antioxidant activity in the early phase of the wound healing process. [10]
In vitro studies [9], Centella leaves are reported to have high antioxidant in 3 pathways
Superoxide free radical activity (86.4%)
Inhibition of linoleic acid peroxidation (98.2%)
Radical scavenging activity, DPPH (92.7%).
In vitro studies using linoleic acid model, ethanolic extract of Centella showed significantly higher antioxidant than the water and negligible amount in petroleum extract, whereas the roots of the plant demonstrated higher antioxidant activity than that of the leaves and petioles [11] .
Beside the triterpenes, the antioxidant protection effect of Centella is contributed by its enriched flavonoids and selenium contents to stimulate cell rejuvenation, improve physical and mental health [12] .
The scavenging activity of Centella water extract was an IC50 value of 31.2 μg/mL, whereas ascorbic acid and butylated hydroxytoluene (BHT) activity were IC50 values of 2.5 and 7.6 μg/mL, respectively [13] . In this context, Centella water extract has the capability to scavenging free radicals due to its phenolics (2.9 g/100 g) and flavonoids (0.36 g/100 g). Antioxidant activity of the crude extract of Centella leaves was comparable to the activities of rosemary and sage |14] .
Neuroprotection effect
Centella extract has been used in Ayurvedic medicine as a nerve tonic. The micronutrients in the extract are reported to be responsible in retarding brain aging and assist in renewal of neural tissue, hence it is effective in enhance memory and revitalize the brain as well as increase attention span and concentration15. Some of these improvement and stimulation effects have been proven experimentally.
Oral supplement of Centella extract had shown effective protection from cognitive deficiency and oxidative stress in rats that resulted in strong memory enhancement effect [16,17] .
Neuroprotective effect of Centella extract was proven to protect monosodium glutamate-induced neurodegeneration [18]. Neuroprotective efficacy on standardized water extract of Centella (5 mg/kg body weight) for 10 days against 3-nitropropionic acid-induced oxidative stress in brain of prepubertal mice enhanced glutathione levels, thiols and antioxidant defenses in brain regions [19,20] .
In the study with elderly volunteers, Centella extract had shown positive modulation of cognition function and improvement of self-rated mood [21] . It is effective in the management of mild cognitive impairment and other related age-related problems of elderly people such as improvement of diastolic blood pressure, peripheral neuritis, insomnia and loss of appetite [22] .
In Ayurvedic medicine and traditional Chinese medicine, Centella has been used for centuries to control anxiety, helps in relaxation and mental calmness [23] . Studies in human and animal models have reported that Centella possesses anxiolytic activity potential. Investigations of the pharmacology effect of Centella in a double- blind, placebo-controlled study have revealed that the 12 g orally intake of Centella extract effectively increase the acoustic startle response (ASR) after 30 and 60 min suggesting the extract potent anxiolytic activity in healthy human subjects which lead to calmness effect [24] . In animal studies, the water extract of Centella containing 84% asiaticoside possess anxiolytic activity by inhibiting phospholipase (PLA.sub.2) activities in rat cerebellum |25] . This group of enzymes has abnormal activity in the central nervous system in some neuropsychiatric diseases and Centella water extract is an excellent candidate as a potential therapeutic agent for neuroinflammation and oxidative stress.
There has not been any study of the negative effects of Centella on neurological systems. However, Sahelian 25 reported that high dose of acetylcholine esterase enzyme, which can be found in Centella may cause side effects including nausea, vomiting, diarrhea, abdominal pain and dyspepsia.
CONCLUSION
Centella asiatica is a very important herbal plant in food and beverages. Its potential as a natural antioxidant extract reflects its capability to become a candidate to prevent oxidative damage, hence promoting health benefits. Many studies especially in animal experiments and in human interventions have shown its wide pharmacological activities in brain improvement and neuroprotection effect. With a very low toxicity as attested by its long popular use as a natural product, Centella can be a potential herbal plant in many healthcare applications.
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