The monoterpene perillyl alcohol (POH) is a naturally occurring compound derived from citrus fruits, mint, and herbs. It exhibited chemotherapeutic potential against various malignant tumors in preclinical models and was being tested in clinical trials in patients with refractory advanced cancers. POH was formulated in soft gelatine capsules and orally administered to cancer patients several times a day on a continuous basis. However, such clinical trials in humans yielded disappointing results, also because of the large number of capsules that had to be swallowed caused hard-to-tolerate intestinal side effects, causing many patients to withdraw from treatment due to unrelenting nausea, fatigue, and vomiting. The clinical trials in Brazil have explored intranasal POH delivery as an alternative to circumvent the toxic limitations of oral administration. In these trials, patients with recurrent malignant gliomas were given comparatively small doses of POH via simple inhalation through the nose. Results from these studies showed, that this type of long-term, daily chemotherapy was well tolerated and effective. The precise mechanism of action is still undetermined, but it is known, that perillyl alcohol plays an important role in the process of hepatoma cell invasion and migration via decreasing the activity of Notch signaling pathway and increasing E-cadherin expression regulated by Snail. Another possible mechanism is included inhibition of Na/K-ATPase (NKA). The NKA α1 subunit is known to be superexpresses in glioblastoma cells (GBM) and POH acts in signaling cascades associated with NKA can control cell proliferation and/or cellular death.

Perilla alcohol is a naturally occurring monoterpene related to limonene. It is isolated from the essential oils of lavender, peppermint, spearmint, cherries, celery seeds, and several other plants. It has been used topically as a mosquito repellant and in toiletries and may be touted as a constituent of natural products such as tart cherry juice. Perillyl alcohol has demonstrated antiangiogenesis and anticancer effects in vitro. Purported mechanism of action is suppression of the synthesis of small G proteins, including RAS, thereby arresting tumor cells in the G1 phase of the cell cycle. Early clinical studies did not efficacy in prostate, ovarian or breast cancer, probably due to bad pharmacokinetic properties and toxicity after oral administration. More recent preliminary studies found intranasal delivery in patients with malignant gliomas to be well-tolerated and effective, with one study reporting tumor size regression, and another reporting increased overall survival and no side effects after long-term use.