Although macroalgae intake is not as prevalent in Europe as in Asia, microalgae have acquired popularity because of their physiologically active components, earning them the reputation of "new superfoods"
[5]. Between 1950 and 2019, global seaweed cultivation and production increased by a thousand-fold, with mainly brown seaweed (from 3.1 million tonnes to 16.4 million tonnes) and red seaweed cultivation (from 1 million tonnes to 18.3 million tonnes) being the main contributors
[1]. However, the world cultivation of green seaweed decreased from 31,000 tonnes to 17,000 tonnes during the same period
[2]. The 16,696 tonnes of green seaweeds grown in 2019 represented only 0.05 percent of the total seaweed production in the same year. Among the 16,696 tonnes produced were
Caulerpa spp.,
Monostroma nitidum,
Enteromorpha [
Ulva]
prolifera,
Capsosiphon fulvescens, and
Codium fragile, all of which are included in FAO’s Aquatic Sciences and Fisheries Information System. Out of 100 known
Caulerpa species, only seven are utilised for human consumption globally, with
C. lentillifera and
Caulerpa racemosa dominating in this aspect
[6].
Table 1 shows the global seaweed production and comparison by region in 2019.
C. lentillifera is an alternative food that can also be used therapeutically. Over the years, it has gained popularity owing to its nutritional value, potential pharmacological benefits, and sustainability
[15][16]). Within the past five years, several publications have reviewed various aspects of
Caulerpa spp., such as its consumption, nutritional value, and farming
[6], bioactive components and biotechnological applications
[17], metabolite roles in cancer treatments
[18], as well as its position as a functional food
[11]. Only two publications had focused on reviewing the green algae genus
Caulerpa in chemical composition, diversity, ecology, farming, pharmacological and industrial potential
[10][19]). However, the review did not critically evaluate
C. lentillifera specifically. To the best of researchers' knowledge, no publication has focused solely on
C. lentillifera in terms of its nutrient content and recent advances in potential health benefits that would make it suitable for pharmaceutical and nutraceutical use.
2. Nutritional Value of C. lentillifera
The proximate composition and the total dietary fibre content of C. lentillifera from different countries are shown in Table 2.
Table 2. Proximate composition and fibre contents of C. lentillifera from different countries.
2.1. Carbohydrate and Fibres
The most abundant component in
C. lentillifera are carbohydrates and dietary fibre. Dietary fibre is a complex mixture of carbohydrates and polymers in plants, including oligosaccharides and polysaccharides. Other non-carbohydrate components such as polyphenols, resistant proteins, saponins, and waxes may also be present
[38]. However, these may vary even within its species
[39]. For instance, although belonging to the same genus and family,
C. lentillifera has higher carbohydrate content than
C. racemosa [40].
C. lentillifera contains as low as 0.36% and as high as 72.9% carbohydrates in its dry matter (
Table 2). Its dietary fibre content is approximately 17.5 to 36.7% in 100 g dried
C. lentillifera, respectively. Water-soluble fibre content is approximately 2.45–17.21%. Water-soluble fibres are usually higher in red algae, around 15 to 22% in the dry matter, such as in
Chondrus crispus (Irish moss) and
Porphyra/Pyropia spp. (nori)
[41][42].
In seaweed, soluble fibres can absorb water up to 20 times its volume
[43]. This helps enhance the binding of water with food pellets in the gut and aids in stool bulking and shortening transit time in the colon; these act as positive factors that may prevent colon cancer
[44]. In
Caulerpa spp., soluble polysaccharides mostly consist of glucans and sulfated polysaccharides
[19]. Sulfated polysaccharides from
C. lentillifera have been reported to have physiological benefits, which will be discussed in the latter part of this research. Insoluble dietary fibres are generally not digested in the human gastrointestinal tract. Upon contact with water, they do not form gels but retain water in their structural matrix, increasing faecal bulk and accelerated intestinal transit
[45]. Insoluble dietary fibres of
C. lentillifera range from 15.75 to 28.98% (
Table 2). However,
C. lentillifera has lower dietary fibre content than other green seaweeds, such as
C. racemosa and
Ulva reticulata, at 65.7% and 64.9%, respectively
[40][46][47]. In adults, high consumption of dietary fibre, particularly fermentable fibres, has been linked with increased short-chain fatty acid (SCFA) contents in the stool
[44][48].
2.2. Protein and Amino Acids
With increased population growth and demand for protein, seaweeds are plausibly viable and sustainable protein sources due to their low environmental impact and fast-growing rate. Furthermore, the protein content of whole algae is very high compared to common food staples such as cereals, legumes, and nuts
[49]. With its versatility and simplicity of usage, whole algal protein has the potential to be a tremendous whole-food protein source, as well as a great way to supplement protein-deficient diets
[50]. When comparing the protein contents, the levels of proteins are higher in Rhodophyta (red), followed by Chlorophyta (green), and Ochrophyta (brown)
[51][52]. The protein content of
C. lentillifera ranged from 0.43 to 19.38% in various countries (
Table 2). The wide difference and instability of the protein content could be affected by various external factors, such as water temperature, season, geography, weather, and other factors
[46]. It was reported that protein content in seaweed was higher in winter than in autumn and summer
[53][54].
The protein quality depends on the presence and quantity of essential amino acids. Amino acids are the building blocks that form proteins bound together via peptide bonds formed between the carboxyl group of an amino acid and the amino group of the next amino acid in line
[55].
C. lentillifera are considered to have high-quality proteins as the essential amino acids present and were close to egg and soya protein content
[54]. Except for tryptophan, almost all essential amino acids (EAA) are present. Their amino acid profile is dominated mainly by leucine, valine, aspartic acid, glutamic acid, and glycine. The major amino acids in seaweed proteins are aspartic and glutamic acid, which contribute to the umami flavour
[56]. The amino acid profile of
C. lentillifera is shown in
Table 3.
Table 3. Amino acid profile of C. lentillifera.
2.3. Minerals
Minerals absent from freshwater algae and terrestrial crops are mostly available in seaweeds
[57]. Minerals are essential and required in certain amounts for the normal metabolic functioning of the human body
[58]. The mineral element found present in
C. lentillifera, including essential minerals and toxic minerals, are presented in
Table 4. The mineral content varies due to the phylum or class of the seaweed and geographical origin, along with seasonal, environmental, and physiological variations
[39].
Table 4. Mineral element composition in C. lentillifera in different countries.
Essential minerals crucial for human wellbeing include Ca, Cu, Fe, Mg, Zn, K, Na, P, Se, Mn, Cr, and I
[60][61]. On the other hand, toxic minerals such as Al, As, Cd, Hg, and Pb do not possess any benefits to humans but cause detrimental effects, which are present in
C. lentillifera [62][63]. As stated in
Table 4, Na, Mg, K, Ca, and Mn has a wide range of concentrations, among all mineral elements, with the highest concentration in Na (14.90–130,794 mg/100 g). For Mg, the highest concentration value was around 8126.59 mg/100 g (in China) to 10,663 mg/100 g (in Vietnam). The highest concentration value of K and Mn were found in
C. lentillifera from China, 4967.34 mg/100 g and 1341.07 mg/100 g.
The calcium content in
C. lentillifera is comparable to common foods such as milk products, meat, fish, poultry, and legumes. For instance, the highest concentration value found in
C. lentillifera was 8137 mg/100 g (in Vietnam) which is 4 times higher than the calcium content in high calcium milk powder, 2000 mg/100 g
[64][65]. Iodine and iron are important to the human diet, both of which can be found in high concentrations in seaweeds, including
C. lentillifera [66]. Insufficiency and deficiency of iodine could lead to goiter and hypothyroidism
[65]. Although the iodine content in
C. lentillifera is relatively low compared to in other green seaweed such as
Ulva clathrata [67], it can be considered a cheap and reasonable option to fulfil the minimum iodine required needed by the body
[65][68].
The deficiency of iron is a major health problem worldwide. The root of this problem is caused by prolonged inadequate intake due to low bioavailability in the diet. Especially during the period of growth and chronic blood loss, the increase in iron requirement may also cause iron deficiency
[65]. The consumption of
C. lentillifera could be a potential iron supplement to combat iron deficiency. However, it is difficult to generalise or conclude whether the mineral contents in
C. lentillifera is high or low, as different sampling region have greatly varied environmental conditions
[19]. From the compiled data in
Table 4, it can be concluded
C. lentillifera are rich in minerals that meet the requirement of the human body. However, the Na/K ratios need careful consideration, as it has been reported to be higher than in other seaweeds such as
Sargassum polycystum and
Eucheuma cottonii [24]. If the Na/K ratio is too high, it is detrimental to the sodium to potassium balance in the human body, which can result in cardiovascular diseases. A simple desalting operation, such as soaking, is recommended before eating
[32].
2.4. Lipids
C. lentillifera are significantly low in lipid content ranging from 0.05 to 14.0% in dry weight. Despite low lipid composition,
C. lentillifera has raised interest due to a high content of long-chain polyunsaturated fatty acids (PUFAs) and carotenoids
[19][41]. Compared to terrestrial vegetables,
C. lentillifera contain significantly higher levels of polyunsaturated fatty acids, which act as strong antioxidants, such as ω-3 and ω-6
[69], which have various roles in the prevention of cardiovascular diseases, osteoarthritis, and diabetes
[70]. The fatty acids profile of
C. lentillifera are shown in
Table 5. The ω-3 and ω-6 PUFAs, particularly linoleic acid (18:2ω6) and 𝛼-linolenic acid (18:3ω3), cannot be synthesised by most heterotrophic organisms and can only be obtained through dietary intake
[32][71]. All these PUFAs can be found in
C. lentillifera, with 𝛼-linolenic acid (18:3ω3) being the most abundant
[71]. The fatty acid compositions of
C. lentillifera are as tabulated in
Table 5.
Table 5. Fatty acids composition in C. lentillifera.
2.5. Vitamins
Seaweeds are known to be a good source of both water-soluble and fat-soluble vitamins. The requirements of vitamin A, B2, B12, and two-thirds of vitamin C in the human body could be fulfilled by consuming 100 g of seaweed
[72][73].
Table 6 indicates the vitamin content found in
C. lentillifera with its daily RNI and daily UL for comparison purposes.
Table 6. Vitamin content in C. lentillifera, the daily recommended nutrient intake (RNI), and the tolerable upper intake level (U.L.) per day.
Water-soluble vitamin C is the most abundant in
C. lentillifera, the major contributor to its antioxidant properties, with concentrations ranging from 0.028–274 mg/100 g. Among other seaweed groups,
C. lentillifera is generally rich in B group vitamins
[74]. Vitamin B1, B2, and B3 were present in
C. lentillifera in trace amounts; however, the amount detected still exceeded the recommended daily intake. The total amount of vitamin B2 in
C. lentillifera is considerably higher than in various legumes, including chickpeas, lentils, red and black grain, and soya beans, which contain relatively high riboflavin levels of around 0.2–0.5 mg/100 g
[64]. Recent data on the riboflavin content of selected commercial rice, such as fragrant rice, basmati rice, and Siam rice, showed that all varieties contain 0.06 mg riboflavin per 100 g
[75]. The amount of B3 in
C. lentillifera, 1.9–200 mg/100 g, was also higher than that of
Ulva fasciata, 1.02 mg/100 g, and
E. flexuosa, 0.98 mg/100 g
[76].
2.6. Pigments
The most abundant pigments in the
Caulerpa species are chlorophylls, mostly composed of chlorophyll a and b
[77]. Chlorophylls have an antioxidant property that makes them useful nutritional and a health supplement
[78]. Chlorophylls available in our diet are obtained via the consumption of green vegetables. Several studies have demonstrated that chlorophylls and their degradation products have anti-proliferative and anticancer properties
[41][79]. Carotenoids which are tetraterpenoid pigments are also found in
C. lentillifera. Most carotenoids were present in seaweeds, such as α- and 𝛽-Carotene, lutein, and zeaxanthin, in which all except α-carotene were detected in
C. lentillifera, as shown in
Table 7.
Table 7. The concentration of pigments found in Caulerpa lentillifera.
β-carotene is a precursor of vitamin A (retinol), an essential vitamin that promotes a healthy immune system, good skin, and eye health
[78].
β-carotene also has antioxidant properties that protect the body from free radicals produced by oxidation of other molecules
[81]. Carotenoids like lutein and zeaxanthin prevent the progress of age-related macular degeneration
[56][82]. Caulerpin is a bis-indole alkaloid found in genus
Caulerpa [83]. In
C. lentillifera, it is found present at concentrations of 25.79–33.59 μg/g. This compound contributes to some of its reported therapeutic activities. For instance, caulerpin isolated from
Caulerpa taxifolia showed anti-diabetic properties
[84], whereas caulerpin sourced from other
Caulerpa spp. demonstrated potential anti-inflammatory and anti-nociceptive properties
[85].