Mangrove extract delivers triterpenes fast in rat pharmacokinetic first

For the first time, researchers have mapped how two medicinally important triterpenoids behave in the bloodstream when they are delivered not as purified laboratory compounds but inside the complex chemical matrix of a living plant. In a study published in Discover Pharmaceutical Sciences, Mayuresh Joshi, Sunita Shailajan and Sasikumar Menon report the simultaneous pharmacokinetic profiling of betulinic acid and ursolic acid absorbed from a standardized extract of the grey mangrove, Avicennia marina, in female Wistar rats. The work provides the first quantitative ADME evidence for this mangrove species and positions its two pentacyclic triterpenoid markers as reliable anchors for standardizing the extract.

Avicennia marina, the grey mangrove, thrives along the Indo-Pacific coastline in one of the most demanding ecological niches on Earth, tolerating high salinity, tidal swings and waterlogged, oxygen-poor soils. That stress has driven the evolution of a rich secondary metabolism, and the plant has long featured in traditional ethnomedicine for conditions ranging from rheumatism and skin disease to hepatic congestion and jaundice. Modern pharmacological attention has converged on its abundant pentacyclic triterpenoids, ursolic acid and betulinic acid, which have been reported in the literature to carry anti-inflammatory, antioxidant, hepatoprotective and, in the case of betulinic acid, selectively cytotoxic activity against melanoma cells.

Both molecules, however, carry a notorious handicap. With log P values typically above 5 and high crystalline lattice energy, they dissolve poorly in water and are absorbed erratically from the gut. Historical pharmacokinetic studies of the purified, unformulated compounds have consistently shown limited systemic delivery: betulinic acid given alone typically peaks late, between two and four hours, with only microgram- or nanogram-level exposure, while pure ursolic acid suffers significant first-pass hepatic metabolism and poor intestinal permeation. The rationale for the new study was the so-called phytocomplex effect, the idea that specialized metabolites travelling alongside natural surfactants such as saponins and polyphenols may dissolve and absorb differently than isolated scaffolds.

To test that idea quantitatively, the team first built a bioanalytical platform. They developed and validated a reversed-phase HPLC method with photodiode array detection according to US-FDA bioanalytical guidelines, using 18β-glycyrrhetinic acid, an oleanane-type triterpenoid absent from the extract, as the internal standard. Plasma samples were cleaned up with a combined protein precipitation and liquid-liquid extraction protocol: acetonitrile precipitated the proteins, ethyl acetate pulled out the lipophilic triterpenoids, and the dried residue was reconstituted for injection onto a C18 column with detection at 205 nanometres.

The method performed well across the full validation battery. Calibration curves were linear from 1.0 to 30.0 micrograms per millilitre, with coefficients of determination of 0.998 for betulinic acid and 0.996 for ursolic acid. The limit of detection was 0.5 micrograms per millilitre for both analytes and the lower limit of quantification was 1.0 microgram per millilitre. Mean extraction recoveries ranged from 83.89 to 84.61 percent for betulinic acid and 84.29 to 85.62 percent for ursolic acid, matrix effects stayed within plus or minus 3 percent across six independent lots of blank rat plasma, and the internal-standard-normalized matrix factor sat near unity at 0.98 to 1.00. Carryover after the upper calibration limit was negligible, dilution integrity back-calculations ranged from 96.12 to 101.45 percent, and stability tests under bench-top and freeze-thaw conditions confirmed the analytes were robust through handling and storage.

The animal experiment itself was designed around ethical and analytical constraints. Twenty-four nulliparous, non-pregnant female Wistar rats, chosen to maintain continuity with the team’s prior OECD Guideline 420 acute toxicity work, were divided into four parallel cohorts of six animals each. After a single oral dose of 2000 milligrams per kilogram of the standardized ethyl acetate leaf extract, a dose set at the extract’s established no-observed-adverse-effect level and equivalent to roughly 2.204 milligrams of betulinic acid and 6.780 milligrams of ursolic acid per rat, blood was drawn at thirteen time points over 24 hours. Because a composite sparse-sampling design was used, with each animal contributing only three to four draws and total blood loss capped at 1.6 millilitres, no individual animal yielded a continuous concentration-time curve. Instead, Phoenix WinNonlin’s sparse-sampling module built a single composite profile from the group means at each time point, and non-compartmental analysis with the linear-up log-down trapezoidal rule produced the pharmacokinetic parameters, reported as composite values with standard errors.

The resulting profiles were strikingly asymmetric. Betulinic acid entered the bloodstream with remarkable speed, reaching a peak concentration of 25.52 plus or minus 0.215 micrograms per millilitre at just 0.33 hours, about twenty minutes after dosing, and then lingered, with a half-life of 4.39 plus or minus 0.419 hours and an elimination rate constant of 0.1578 per hour. Ursolic acid behaved almost as a mirror image: it peaked later, at 2.00 hours, at 29.12 plus or minus 0.498 micrograms per millilitre in the abstract-reported values, but cleared faster, with a half-life of 2.20 hours and an elimination rate constant of 0.3147 per hour. Ursolic acid also delivered the higher total exposure, with an area under the curve from zero to infinity of 141.22 plus or minus 1.615 micrograms per millilitre times hours. Together the two kinetics produced a sustained systemic presence of triterpenes spanning roughly an eight-to-ten-hour window.

The most intriguing observation is what the authors call a dosage-to-exposure paradox. Betulinic acid was administered at roughly one-third the amount of ursolic acid, yet the two compounds reached nearly identical peak plasma concentrations. The team proposes a mechanistic hypothesis: betulinic acid carries its carboxylic acid group at the C-28 position of its lupane skeleton, while ursolic acid carries it at C-17 on the ursane skeleton with a different arrangement of methyl groups, and the extract’s endogenous amphiphiles, saponins and plant lipids, may form mixed micellar structures that preferentially solubilize betulinic acid’s architecture, accelerating dissolution and passive diffusion across the gastric and upper duodenal mucosa. The authors are careful to frame this as a hypothesis; no parallel arm dosing the pure isolated compounds was run in this study, so the comparison rests against historical literature values rather than a head-to-head trial.

The authors are equally candid about the study’s limits. The exclusive use of female rats, while methodologically justified, restricts generalizability, since sex-specific differences in cytochrome P450 expression and gastrointestinal transit could shift triterpenoid absorption and clearance in males. The single high dose, chosen because lower extract doses would push plasma levels below the validated UV detection limit, leaves dose-proportionality unexplored, and the absence of an intravenous arm means absolute oral bioavailability could not be calculated. The authors note that LC-MS/MS, the gold standard for trace-level bioanalysis, would be needed to characterize kinetics at lower, more traditional dose ranges, and they flag intravenous studies, chronic-dose profiling and nanocarrier formulations such as phytosomes or self-emulsifying systems as the critical next steps.

Even with those caveats, the study marks a shift from qualitative observation to quantitative pharmacology for a plant long confined to ethnomedical records. By demonstrating that the mangrove’s native phytochemical environment can deliver lipophilic triterpenoids into systemic circulation with fast, measurable and reproducible kinetics, the work establishes betulinic acid and ursolic acid as pharmacokinetic markers for standardizing Avicennia marina extracts, and offers a concrete analytical template for testing whether the phytocomplex effect holds up under the stricter head-to-head trials that will decide whether mangrove-derived triterpenoids can move from traditional remedy toward standardized phytopharmaceutical.

Subject of Research: Pharmacokinetic profiling of betulinic and ursolic acids from Avicennia marina extract in rats

Article Title: Simultaneous determination and ADME profiling of betulinic and ursolic acids from Avicennia marina in Wistar rats

Article References: Joshi, M., Shailajan, S., & Menon, S. (2026). Simultaneous determination and ADME profiling of betulinic and ursolic acids from Avicennia marina in Wistar rats. Discover Pharmaceutical Sciences, 2(1), Article 16. https://doi.org/10.1007/s44395-026-00052-6

Image Credits: AI Generated

DOI: 10.1007/s44395-026-00052-6

Keywords: Avicennia marina, grey mangrove, betulinic acid, ursolic acid, pharmacokinetics, RP-HPLC-PDA, Wistar rats, sparse sampling, triterpenoids, ADME, bioanalytical validation, phytocomplex