Limonene - Research

Limonene can be found in high concentrations in citrusy fruits like oranges and lemons. Limonene can work wonders on mood and stress, providing an uplifting sense of calmness.  

Limonene Effect and Benefits
• Elevated mood
• Stress relief
• Anti-cancer
• Mood enhancer
• Improves depression
• Anti-bacterial

Limonene is a monocyclic monoterpene and as the name suggests, it's found in citrusy fruits like oranges and lemons. Limonene is also found in varieties of cannabis with citrusy aromas. Limonene is highly absorbed by inhalation and quickly enters the blood stream. It assists in the absorption of other terpenes through the skin and other body tissue. Therefore combination with other terpenes will allow for an increased effect of those terpenes. 
Limonene promotes a general uplift in mood and attitude by the entourage effect. This compound is also used in diets aimed at weight reduction, in the treatment of ulcers and gastric reflux, as an antiseptic and an insect repellent. There are also undergoing trials for using limonene to treat depression and anxiety: during testing on the effects of limonene, participants experienced an increase in attention, mental focus, well-being and even libido. A 2011 study conducted at the University of Arizona and published in the journal Oncology Reviews found that limonene contributes to modulate the body's immune system, resulting in an anti-cancer effect. A 2013 study by the same university and published in the journal Cancer Prevention Research found limonene effective in preventing cancer cell proliferation and reducing tumor size. 

Limonene demonstrated increased social interaction time and decreased immobility time, in the forced swim test using mice, indicating anxiolytic and antidepressant effects. The effects were comparable with the traditional anxiolytic diazepam and the antidepressant fluoxetine. 
Limonene attenuates anxiogenic and depression like effects of corticotropin releasing factor in mice (PDF) 

Limonene was evaluated against human eosinophilic leukemia cells, specifically looking at reactive oxygen species (ROS), monocyte chemoattractant protein-1 (MCP-1), nuclear factor (NF) kappa B, and p38 mitogen-activated protein kinase. Limonene was found to inhibit cytokine and ROS production, while inactivating eosinophil migration. 
Anti-inflammatory Effects of Limonene from Yuzu (Citrus junos?Tanaka) Essential Oil on Eosinophils 

Limonene has been attributed to induction of phase I and phase II enzymes that result in carcinogen detoxification. In two prostate cancer cell lines, limonene administration resulted in higher ROS generation, depletion of GSH, accompanied by increased caspase. In addition limonene results in differentiation of cancer cells as well. Breast and pancreatic cancer cell lines were also negatively affected. 
Antitumorigenic effects of limonene and perillyl alcohol against pancreatic and breast cancer. 
Chemoprevention and therapy of cancer by d-limonene. 
d -Limonene sensitizes docetaxel-induced cytotoxicity in human prostate cancer cells: 
Generation of reactive oxygen species and induction of apoptosis