Hikau-hikauan is a shrub or tree reaching a height of 20 meters or less, with the trunk reaching a maximum diameter of 50 centimeters. Leaves are very thick, leathery, oblong to elliptic-oblong, 4 to 10 centimeters long, 2 to 4 centimeters wide, somewhat pointed at the tip, and tapering to a nearly blunt base. Flower is solitary. Calyx is green, 2.5 to 3 centimeters long, and comprises six segments which are longer than the tube. Petals are six, linear, pink or white, about as long as the calyx- segments. Fruit is hard, rounded-depressed, 3 to 4 centimeters in diameter, surrounded nearly to the middle by the calyx-tube; the persistent lobes are spreading. Seeds are numerous.
- Along small tidal streams near the limits of salt or brackish water; rarely on the open beach.
- Occurs in China, Malaysia, Indonesia, Singapore, Sri Lanka, Vietnam and Thailand.
- Bark contains a moderate proportion of tannin.
- Yields active constituents: phenolic compounds such as gallic acid and two flavonoids luteolin and luteolin 7-O-ß-glycoside.
- Study of stems and twigs isolated twenty-four compounds, including 8 steroids (1-8), nine triterpenoids (9-16,24), three flavonoids (20-22), and four benzenecarboxylic derivatives (17-19, 23).
(see study below) (8)
- Phytochemical screening of bark tissue yielded high amounts of phenolics, flavonoids, tannins, alkaloids, and saponins.
- Study of petroleum ether extracts of roots isolated two compounds: lupeol (C30H50O) and betulinaldehyde (C30H50O2).
- Fruit is slightly acid.
- Considered astringent and antiseptic.
- Reported antioxidant and cytotoxic.
Edibility / Culinary
- Fruit eaten raw or cooked.
Fruit, slightly acidic, used as food; also for making vinegar.
- Leaves consumed in certain areas.
- Fruit used to flavor curries and chutnies.
- Fruit used as poultice in sprains and swellings.
- Used for piles.
- Fermented juice useful in arresting hemorrhage.
- Wall of old fruit used as vermifuge.
- Half-ripe fruits used for treating cough.
- Air roots used for making wooden soles of women's slippers (korcho) and of bottle stoppers.
- Referred to as corktree, because fishermen make fishing net floats out of the pneumatophores.
- Wood also used as firewood.
• Antimicrobial / Cytotoxicity: Study isolated nine compounds from the fruits of S caseolaris. Screened against a rat glioma C-6 cell line, compounds 1, 2 and 6 were found to show moderate cytotoxic activity and suggests a potential foundation for further chemotaxonomic studies. (1)
• Flavonoids / Antioxidant: Study yielded two flavonoids, luteolin and luteolin 7-O-B-glucoside. Both compounds showed to possess antioxidant activity. (2)
• Antioxidant: Of 57 samples of 32 species tested, the calyces of Sonneratia caseolaris exhibited strong antioxidant activity followed by stamens of S. caseolaris. It also exhibited strong anti-lipid peroxidation. (3)
• Antimicrobial / Seed: A methanolic seed extract showed inhibition of Staphylococcus aureus and Candida albicans. Gallic acid showed activity against only S. aureus. Tested extracts showed antibacterial activity against Propionibacterium acnes. (6)
• Oleanolic Acid / Antihyperglycemia / α-Glucosidase Inhibitory Activity / Fruits: A methanolic extract of fruit of Sonneratia caseolaris showed moderate intestinal α-glucosidase inhibitory. Study isolated three compounds: oleanolic acid, ß-sitosterol=ß-D-glucopyranoside and luteolin. (7)
• Cytotoxicity / Stems and Twigs: Study of stems and twigs isolated 24 compounds. In in-vitro cytotoxic assay against SMMC-7721 human hepatoma cells, compound 21 (3′,4′,5,7-tetrahydroxyflavone) exhibited significant activity. (see constituents above) (8)
• Cytotoxic Compounds / Fruits: Study isolated nine compounds from the fruit of S. caseolaris. (-)-(R)-nyasol (1), (-)-(R)-40-O-methylnyasol (2) and maslinic acid (6) were found to show moderate cytotoxic activity against a rat glioma C-6 cell line. (9)
• Antinociceptive / Antioxidant / Leaves: Study evaluated an ethanolic extract of leaves for antinociceptive and antioxidant activities. Results showed statistically significant writhing inhibition in acetic acid induced writhing model in white albino mice. On DPPH scavenging assay, the antioxidant activity was comparable to standard ascorbic acid. (10)
• Antimicrobial / Antioxidant / Bark: Study suggests Sonneratia caseolaris bark is a potential source of bioactive compounds with stable antimicrobial and antioxidant properties, with potential for use as antimicrobial/antioxidative agents for clinical, pharmaceutical and food processing applications. (11)
• Antinociceptive / Antidiarrheal / Leaves: Study screened a crude ethanol extract of leaves for antinociceptive and antidiarrheal activities. Results showed significant writhing inhibition in acetic induced writhing in mice, with diclofenac sodium as standard drug. In castor oil induced diarrhea in mice, there was increased latent period and significant decrease in frequency of defecation. Loperamide was used as standard. (12)
• Anticholinesterase Activity: Tacrine, stamen extract and seed extract by maceration using methanol showed noncompetitive inhibition on acetylcholinesterase activity., while luteolin, luteolin glycoside and calyx extract seed extract showed partial noncompetitive inhibition on acetylcholinesterase activity. (13)
• Antimicrobial / Antioxidative: Study evaluated the antioxidative (DPPH) and antimicrobial (Bacillus subtilis, B. coagulans, Escherichia coli, Proteus vulgaris and Saccharomyces cerevisiae) properties of various S. caseolaris bark extracts. Results showed the SC bark as a potential source of bioactive compoounds with stable antimicrobial and antioxidant properties. (16) In a study of 52 traditionally used Thai medicinal plants, S. caseolaris showed potential antioxidant activity and antimicrobial activity against Pseudomonas aeruginosa and Candida albicans. (17)