Mastiha is a natural product of the Mediterranean basin with several health benefits due to its bioactive compounds, namely terpenes, phenolic compounds, phytosterols, arabino-galactanes proteins. It appears as a dried resinous exudate from stems and branches of the tree Pistacia lentiscus (Pistacia lentiscus L. var latifolius Coss or Pistacia lentiscus var. Chia).
1. Introduction
Mastiha, is a natural product of the Mediterranean basin coming as a dried resinous exudate from stems and branches of the tree
Pistacia lentiscus (
Pistacia lentiscus L. var
latifolius Coss or
Pistacia lentiscus var.
Chia). It consists of a plethora of bioactive constituents, including phenolic compounds, phytosterols, arabino-galactanes proteins, and 30% of a natural polymer (poly-β-myrcene)
[1][2][3]. However, Mastiha is a concentrated source of terpenes, such as monoterpenes (i.e., α-pinene, β-pinene, β-myrcene) (
Figure 1) and triterpenes (i.e., mastihadienonic, isomastihadienonic) (
Figure 2).
Figure 1. Major monoterpenes of Mastiha. (a) isomers of α-pinene; (b) β-pinene; (c) β-myrcene.
Figure 2. Major triterpenes of Mastiha. (a) Mastihadienonic acid; (b) Isomastihadienonic acid.
Apart from its culinary usages, Mastiha is known since antiquity for its therapeutic properties documented for the first time by the ancient Greek physicians Hippocrates, Dioscorides and Galenos. Mastiha has been used by medical practitioners and botanists have used it for more than 2500 years mainly for the treatment of stomach and intestine disorders such as gastralgia, dyspepsia and peptic ulcer.
The European Medicines Agency has recognised Mastiha as a herbal medicinal product for the following indications, (a) mild dyspeptic disorders, and (b) symptomatic treatment of minor inflammations of the skin and as an aid in healing of minor wounds
[4].
As there is an increasing consumer’s interest for natural products as preventing and healing factors without side effects, the research interest upon the favourable effects and the mechanisms of action of natural products has increased as well. Regarding Mastiha, several researchers have investigated its antibacterial
[5], antioxidant
[6], anti-inflammatory
[7], cytotoxic
[8], hypolipidaemic activity
[9] and the influence on liver and gut health
[10][11].
2. The Antioxidant Properties of Mastiha
Oxidative stress occurs when oxygen/nitrogen radical levels exceed levels of antioxidants, either due to increased formation or due to deficiency or increased loss of enzyme and non-enzyme antioxidants. Reactive oxygen and nitrogen species (ROS and RNS) can induce severe oxidative damage to macromolecules that leads to cellular dysfunction. Oxidative stress seems to activate inflammatory pathways leading to transformation of a normal cell to tumor cell, tumor cell survival, proliferation, chemoresistance, radioresistance, invasion, angiogenesis and stem cell survival
[12]. Many types of cancer are associated with oxidative stress such as breast, lung, ovarian and leukemia. Also, high levels of ROS and reduced antioxidant defense systems lead to insulin resistance and diabetes
[13]. Additionally, oxidative stress is involved in the pathogenesis of hypertension, whereas risk factors for atherosclerosis can increase the production of free radicals from vascular endothelial cells and smooth muscle cells, thus increasing oxidative stress in the vessels and resulting in endothelial dysfunction. Increased vascular production of ROS is responsible for the production of oxLDL that critically contributes to the pathogenesis of atherosclerosis
[14]. A highly complex antioxidant defense system in human body includes both endogenous and exogenous antioxidant molecules that function interactively and synergistically to neutralise free radicals. Antioxidant enzymes catalyse free radical quenching reactions, metal binding proteins sequester free iron and copper ions catalyze oxidative reactions, and dietary plant-derived antioxidants either neutralise free radicals or enhance endogenous antioxidant activity. There is adequate evidence that bioactive compounds in plant foods may result in a reduction of oxidative stress. Crude plant materials or extracts obtained from plants are of wide scientific interest to further include either the whole extract or the drastic compound to complementary medicine supplements. Use of culinary herbs and medicinal plants has been a treatment approach utilised since ever for the prevention and/or treatment of diseases in humans. Used either as foods in daily nutrition or as components in dietary supplements, medicinal plants are valuable sources of bioactive compounds.
2.1. Preclinical Studies
The antioxidant activity of Mastiha and specifically of the crude resin obtained from the trunk of the tree
Pistacia Lentiscus was first manifested by an in vitro study of Andrikopoulos and colleagues
[15]. Inhibition of the oxidative modification of human LDL by copper sulphate was measured in different extracts from several resins and, overall, Mastiha proved to be the most effective in protecting the LDL particle. The most active extract was that of methanol/water, a common solvent combination applied to isolate polar constituents from natural products, such as phenolic compounds. Also, individual fractions of the resin were investigated to determine the most bioactive as regards antioxidant activity. Mastiha oil, collofonium like residue and the acidic fractions of NaOH and Na
2CO
3, were potent inhibitors of LDL oxidation, whereas the neutral fraction and the acidic emulsion were both quite inactive. In continuation to the previous, the investigation of the molecular mechanisms underlying the antioxidant and antiatherogenic effect of the polar extract from the resin was investigated
[6]. The extract from Mastiha exhibited a potent antioxidant activity restoring glutathione levels in mononuclear cells under oxLDL-induced oxidative stress. The total extract inhibited both apoptosis and necrosis and downregulated the mRNA expression levels of scavenger receptor CD36, thus inhibiting oxLDL accumulation in monocytes. Interestingly, the triterpenoid fraction of the resin rather than the phenolic one demonstrated remarkable increase in intracellular glutathione. When enlightening Mastiha’s effect in activated macrophages, crude resin solubilised in dimelthyl sulfoxide was found to inhibit the nitric oxide (NO) production in lipopolysacharide-stimulated RAW264.7 cells by inhibiting iNOS rather than reducing the radical intensity of NO, while it did not scavenge O2- that is known to counteract NO. On the other hand, a liquid form consisting of crude Mastiha and coconut oil at the ratio of 3:7 scavenged the hydroxyl radical generated by the Fenton reaction in activated macrophages
[16]. Similarly, weak 1,1-diphenyl-2-picryl hydrazyl radical scavenging activities were observed in the study of Mahmoudi and colleagues, however, it showed good Fe
2+ chelating ability
[17]. It is apparent that Mastiha is mediating the regulation of antioxidant defense via pathways other than the radical scavenging. The general antioxidant activity of Mastiha via a non-radical scavenging mechanism has been also proposed by Triantafyllou and colleagues in 2011
[18]. In stimulated smooth muscle cells and endothelial cells Mastiha was proven to decrease the superoxide production associated with downregulation of NADPH oxidase activity, most probably due to inhibition of protein kinase C
[18]. The evidence that in Mastiha treated mononuclear cells a glutathione restoration was reported
[6] and that glutathione inhibits protein kinase C by a non-redox mechanism
[19] indicates the protein kinase C pathway for the antioxidant activity of Mastiha.
In addition to the above, in normally fed experimental rabbits at different time points of ischemia and reperfusion Mastiha significantly decreased levels of malonaldehyde measured as an index of lipid peroxidation. Although in cholesterol fed rabbits Mastiha did not affect malonaldehyde levels, however it exhibited potent antiatheromatic and hypolipidemic activities
[20].
Table 1 summarises the preclinical evidence on antioxidant and anti-inflammatory properties of Mastiha.
Table 1. Preclinical evidence of the antioxidant and anti-inflammatory effects of Mastiha.
Reference |
Experimental Design |
Biomarker |
Effect |
Antioxidant Effects |
[6] |
Mononuclear cells under oxLDL-induced oxidative stress 2.7, 27 and 270 μg of the Folin Ciocalteau reactant substances in polar extract per mL of culture medium |
Glutathione levels |
↑ |
CD36 expression |
↓ |
[15] |
Copper sulphate induced LDL oxidation Methanol/water or hexane extract from 2.5, 5.0, 10.0, 25.0 and 50.0mg Mastiha resin (normal and liquid type collections) and fractions (neutral fraction, acidic emulsion, acidic fractions) |
Thiobarbituric acids reactant substances |
↓ |
[16] |
LPS-stimulated macrophages RAW264.7 Solid (0–100 μg/mL) and liquid (0–0.5%) types of Mastiha in culture medium |
O2 radical scavenging |
- |
OH radical scavenging |
↓ |
NO and prostaglandin E2 |
↓ |
Inducible NO synthase and cyclooxygenase-2 |
↓ |
[17] |
Carrageenan-induced paw edema in rats Mastiha at 200–800 mg/kg administered intraperitoneally 1 h before carrageenan injection |
NO |
↓ |
1-diphenyl-2-picryl hydrazyl radical scavenging |
↓ |
Carrageenan induced edema |
↓ |
[18] |
TNF-α stimulated smooth muscle cells, angiotensin II stimulated endothelial cells Mastiha resin at 0.1–10 μg/mL |
Superoxide and H2O2 |
↓ |
NADPH oxidase activity |
↓ |
[20] |
Experimental ischemia/reperfusion in normal-fed rabbits 46 mg/kg−1/day of Mastiha total extract without polymer or the neutral Mastiha fraction in the form of sunflower oil solution orally administered with habitual diet for 6 weeks |
Malonaldehyde |
↓ |
[20] |
Experimental atherosclerosis in cholesterol-fed rabbits 46 mg/kg−1/day of Mastiha total extract without polymer or the neutral Mastiha fraction in the form of sunflower oil solution orally administered with cholesterol enriched diet for 6 weeks |
Malonaldehyde |
- |
Anti-Inflammatory Effects |
[2] |
Pull-down experiments with Helicobacter pylori neutrophil-activating protein and neutrophils 5 g Mastiha mixed with 0.1 mol/L NaCl, 20 mmol/L Tris–HCl to extract arabinogalactan proteins |
Neutrophils activation |
↓ |
[7] |
Experimental TNBS-colitis in rats 50–300 mg kg−1/day Mastiha administered orally for 3 days |
TNF-α, ICAM-1, IL-6, IL-8 in colonic tissue |
↓ |
Colonic damage |
↓ |
[21] |
TNF-α stimulated human aortic endothelial cells 25–200 μg/mL (for Mastiha extract) and 1–100 μM (for tirucallol) |
VCAM-1 expression |
↓ |
ICAM-1 expression |
↓ |
Phosphorylation of NF-κB p65 |
↓ |
Binding of U937 cells |
↓ |
[22] |
OVA induced allergic asthma in mice 50 or 100 mg kg−1 dissolved in 1% DMSO in saline administered intraperitoneally 4 h before challenge |
Number of infiltrating eosinophils |
↓ |
IL-5, IL-13, eotaxin, eotaxin2 levels in BALF |
↓ |
Eotaxin-induced eosinophil chemotaxis |
↓ |
[23] |
Co-cultured human colon epithelial HT29 cells and monocytes/macrophages Mastiha at 0–150 ng/mL culture medium or respective Acidic or Neutral fraction |
Expression of IL-8 and NF-κB p65 |
↓ |
LDH release from the HT29 cell monolayer |
↓ |
[23] |
Experimental TNBS-colitis in rats 100 mg kg−1/ day of Mastiha or respective Acidic or Neutral fraction administered orally for 3 days |
TNF-a, ICAM-1, IL-6, IL-8 in colonic tissue |
↓ |
Colonic damage |
↓ |
[24] |
Experimental hypertension in rats Mastiha administered at 40 mg kg−1/day per os for 2 weeks |
CRP, IL-6 |
↓ |
2.2. Clinical Studies
Although medicinal plants are used for several disorders, the clinical data supporting the applied practices is often limited. As regards Mastiha, the clinical designs aim mostly at exploring its efficacy in biochemical markers of atherosclerosis and cardiovascular disease progression. As such, it has been reported that Mastiha exhibits a cardioprotective activity as it decreases serum lipids and glucose when administered daily in doses ranging from 2 to 10 g
[25][26].
Focusing on biomarkers of oxidative stress, most recently, we assessed levels of oxLDL and serum antioxidant capacity in an open-label and single arm postprandial study of absorption and bioavailability of Mastiha’s terpenes in healthy adults. Results indicated the bioavailability pattern of targeted triterpenes after oral administration of Mastiha and the potential of these to mediate antioxidant defense in vivo. The increase in triterpene concentration followed an increase in serum antioxidant capacity and a decrease in oxLDL
[27].
In inflammatory bowel diseases (IBD) chronic inflammation of the intestinal mucosa induces ROS/RNS overproduction leading to oxidative stress
[28][29]. Οxidative stress has been considered as both a putative causal and perpetuating factor playing a crucial role in the pathogenesis, progression, and severity of IBD
[30]. When patients with active IBD, both Crohn’s disease (CD) and ulcerative colitis (UC) were randomised to a double-blind and placebo-controlled trial with Mastiha, a decrease in serum oxLDL and oxLDL/LDL or oxLDLD/HDL was reported in patients under Mastiha supplementation
[31]. Additionally, cysteine, was found significantly lower in the placebo arm versus verum arm whereas it correlated negatively with levels of oxLDL. Since cysteine is a precursor of glutathione, the above finding is significant and coincides with the in vitro findings that Mastiha’s antioxidant efficacy involves glutathione synthesis.
Another recent study assessed the acute effects of Mastiha on peripheral and aortic haemodynamics and changes in gene expression of molecules involved in hypertension pathways. A total of 27 subjects (13 hypertensive patients) participated in a randomised double-blind case controlled crossover study with 2.8 g of Mastiha or placebo. Gene expression analyses in mononuclear cells showed that Mastiha administration in hypertensive patients decreased the expression of the pro-oxidant NOX2 genes as well as of the proteasomal (PSMB6, PSMB7, RPN6) and chaperone HSP27. When compared with controls, NOX2 expression in hypertensive patients significantly decreased indicating that Mastiha exhibits regulatory effects on genes involved in pro-oxidant pathways
[32].
Until today and based on the limited data available, it seems that most possibly Mastiha exhibits its antioxidant activity through the protein kinase C pathway rather through the radical scavenging properties of the contained phytochemicals. Further studies are required to shed light on the mechanism underlying these effects. Table 2 summarises the clinical evidence on antioxidant and anti-inflammatory properties of Mastiha.
Table 2. Clinical evidence of the antioxidant and anti-inflammatory effects of Mastiha.
Reference |
Experimental Design |
Biomarker |
Effect |
[33] |
Pilot, active CD patients (N = 10) and healthy (N = 8), 2.2 g of Mastiha daily, 4 weeks |
Plasma CRP, IL-6 |
↓ |
Plasma TNF-α, MCP-1 |
- |
[34] |
Pilot, active CD patients (N = 10) and healthy (N = 8), 2.2 g of Mastiha daily, 4 weeks |
TNF-α secretion from PBMC |
↓ |
MIF release |
↑ |
Plasma IL-6, MCP-1 |
- |
[2] |
Healthy volunteers (N = 3) and H. pylori positive patients (N = 5), 1 g of Mastiha daily, 2 months |
Neutrophil activation |
↓ |
[32] |
Double-blind, case-controlled, crossover study (N = 27), 2.8 g of Mastiha (acute administration) |
Gene expression of pro-oxidant NOX2 genes |
↓ |
[31] |
Open-label, single arm, postprandial study, healthy (N = 17), 10 g of Mastiha |
Plasma oxLDL |
↓ |
Serum antioxidant capacity |
↑ |
[35] |
Double-blind, placebo-controlled, parallel arm RCT, IBD patients in remission (N = 68), 2.8 g of Mastiha daily, 6 months |
Serum IL-6, faecal calprotectin & lactoferrin |
↑ in placebo |
Faecal lysozyme, Serum IL-10 & CRP |
- |
Plasma valine, proline, alanine, glutamine, tyrosine |
↑ in placebo |
[31][36] |
Double-blind, placebo-controlled, parallel arm RCT, IBD patients in relapse (N = 60), 2.8 g of Mastiha daily, 3 months |
oxLDL |
↓ in verum |
Plasma cysteine |
↓ in placebo |
Faecal lysozyme |
↓ in verum |
Faecal calprotectin and lactoferrin |
↑ in placebo |
Serum IL-6 |
↑ in both arms |
Serum IL-10 & CRP |
- |
Plasma fibrinogen |
↓ in verum |