Cell experiment:

RAW 264.7 cells are seeded in 96-well culture plates at a density of 1×105 cells/mL and after incubation for 24 h, are treated with OPE1 (300 μg/mL or 400 μg/mL), OPE2 (20 μg/mL or 40 μg/mL), or Maslinic acid (10 μM or 20 μM) , as well as with/without LPS at the same time. Cell viability i determined using the WST-1 reagent. Briefly, WST-1 reagent (10 μL) is added to each well and incubated for 1h in a humidified incubator. The absorbance of the samples measured at 450 nm (reference wavelength is 750 nm). Viability is expressed as a percentage of the absorbance measured in LPS-treated cells[1].

Animal experiment:

Mice[1]Five-week-old male Balb/c mice (19-21 g) are housed in a conventional condition and provided with the free access to standard rodent chow and water. Edema is induced by intraplantar injection of 100 μL 1% carrageenan into the hind left paw. Maslinic acid is tested initially at a dose of 200 mg/kg, orally administered 60 min before and after carrageenan injection. Paw thickness is measured using electronic digital calipers, 2, 3, and 4 h following carrageenan treatment. Mice are sacrificed by carbon dioxide inhalation 4 h after carrageenan injection[1].

Maslinic acid is a pentacyclic triterpene existed in the protective wax-like coating of the leaves and fruit of Olea europaea L [1]. Maslinic acid is an inhibitor of NO, H2O2, IL-6 and TNF-α.

In HT29 colon-cancer cells, treatment with maslinic acid significantly inhibited cell proliferation in a dose-dependent manner with the IC50 value of 28.8 ± 0.9 μg/mL. Maslinic acid inhibited the expression of Bcl-2 whilst increasing that of Bax. Maslinic acid stimulated the release of mitochondrial cytochrome-c and ativated aspase-9 and caspase-3 [1]. Maslinic acid inhibited the activity of serine proteases, key enzymes necessary for the spread of HIV within an individual's body. Maslinic acid decreased the cytopathic effect and p24 antigen levels in MT2 cells [2].

In KK-Ay mice, an animal model of genetic type-2 diabetes, oral administration of MA (10 mg/kg) reduced the blood glucose levels. Administration of maslinic acid (10 mg/kg and 30 mg/kg) for 2 weeks significantly reduced the blood glucose levels [3]. Pretreatment with MA attenuated ischemia-induced translocation of NF-κB p65 subunit to the nucleus [4].

References:
[1] Reyes-Zurita F J, Rufino-Palomares E E, Lupiáez J A, et al. Maslinic acid, a natural triterpene from Olea europaea L., induces apoptosis in HT29 human colon-cancer cells via the mitochondrial apoptotic pathway[J]. Cancer letters, 2009, 273(1): 44-54.
[2] García, A. Compound from olive-pomace oil inhibits HIV spread. 070709111536, 1-1 (2007).
[3] Liu J, Sun H, Duan W, et al. Maslinic acid reduces blood glucose in KK-Ay mice[J]. Biological and Pharmaceutical Bulletin, 2007, 30(11): 2075-2078.
[4] Guan T, Qian Y, Tang X, et al. Maslinic acid, a natural inhibitor of glycogen phosphorylase, reduces cerebral ischemic injury in hyperglycemic rats by GLT‐1 up‐ egulation[J]. Journal of neuroscience research, 2011, 89(11): 1829-1839.