Chapter 17 The central nervous system
However, for milder psychiatric conditions, phytotherapy can provide useful support. The prevalence of mental health problems, particularly depression and anxiety, in the general population is around one in six people, and around 40% of people with mental health problems will have symptoms of both anxiety and depression. Depression is more common in women than men; around one-half of women and one-quarter of men will be affected by depression at some time. However, other than in mild cases, these disorders are not suitable for self-treatment, and medical supervision is necessary. Sleep disturbances, such as insomnia and early morning awakening, are characteristic of depression and anxiety, although they can also occur independently of mental health problems. Around one-third of adults are thought to experience insomnia, and most do not seek treatment from a physician. Phytotherapy has a role to play in helping to re-establish a regular pattern of sleep. Valerian (Fig. 17.1), for example, has been advocated as a means of alleviating the symptoms of benzodiazepine withdrawal.
Hypnotics and sedatives
Hops, Humulus lupulus L. (Humuli lupuli strobuli) ![image](/wp-content/uploads/2017/04/B9780702033889000173_icon01-9780702033889.jpg)
Constituents
The main active constituents of hops are the bitter principles found in the oleo-resin. These include the α-acid humulone and the β-acid lupulone, and their degradation products, such as 2-methyl-3-buten-2-ol (Fig. 17.2). Other constituents include flavonoids, chalcones, tannins and volatile oils.
Therapeutic uses and available evidence
Modern pharmaceutical uses of hops include sleep disturbances and restlessness. Sedative and hypnotic activities have been documented in vivo (mice) for extract of hops, and for the bitter acid degradation product 2-methyl-3-buten-2-ol. Clinical studies provide some evidence of the hypnotic effects of hops given in combination with the herbal sedative, hypnotic valerian (Zanoli and Zavatti 2008). Antibacterial and antifungal activities have been documented in vitro for certain constituents of hops. Hops are non-toxic, as their use in beer would suggest. Cheers!
Lemon balm, Melissa officinalis L. (Melissae folium) ![image](/wp-content/uploads/2017/04/B9780702033889000173_icon01-9780702033889-1.jpg)
Therapeutic uses and available evidence
Sedative and antispasmodic effects have been documented for melissa extracts using in vivo studies (mice, rats). It is used for nervous or sleeping disorders and functional gastrointestinal complaints. There has been no clinical investigation of the sedative effects of melissa alone in individuals with sleeping disorders. However, clinical trials have explored the effects of melissa in combination with other herbal sedatives (e. g. valerian and hops) and provide some evidence to support the sedative and hypnotic effects of such preparations. Antihormonal effects of balm, mainly antithyroid, have been documented and, recently, cholinergic activity has been found for extracts using human cerebral cortical cell membrane homogenates. Dried lemon balm is usually taken internally in the form of a herbal tea, at a dose of 2–4 g three times a day. Melissa extracts are also applied topically in cases of Herpes simplex labialis resulting from HSV-1 infection (see anti-infectives). Lemon balm is regarded as non-toxic, although it should not be used to excess because of the reputed antithyroid activity. For review, see Ulbricht et al 2005.
Kava, Piper methysticum Forst. (Piperis methystici rhizome)
Piper methysticum (Piperaceae), also known as kava-kava or kawa, has been used in the Pacific Islands, notably Fiji, for hundreds of years. It is a small shrub with heart-shaped leaves and thick, woody roots and rhizomes, which are ground or chewed to release the actives. These are then fermented to make the ceremonial drink Kava, which induces a relaxed sociable state, and is given to visiting dignitaries (including the Pope and the Queen of England). Kava is used medicinally for its tranquillizing properties and numerous other disparate complaints. Recent safety concerns have resulted in Kava products being withdrawn from sale at present (2011), but moves are being made to try to re-introduce it into the EU (Sarris et al 2011).
Therapeutic uses and available evidence
In vitro studies have previously provided some conflicting data on receptor interactions of kava extract and isolated kavalactones. Current thinking is that kavalactones potentiate GABAA receptor activity. Other receptor binding studies demonstrate no interaction with benzodiazepine receptors. The efficacy of kava extracts in relieving anxiety is supported by data from several randomized, placebo-controlled, clinical trials, for example an aqueous kava preparation produced significant anxiolytic and antidepressant activity and appeared equally effective in cases where anxiety is accompanied by depression (Sarris et al 2009). Overall, studies indicate reductions in anxiety after 4–12 weeks of treatment with kava extracts at dosages equivalent to 60–240 mg of kavalactones daily.
Kava extracts are generally well tolerated when used at recommended doses for limited periods. However, kava-induced liver injury has been demonstrated in several patients worldwide, and it has been suggested that this is due to inappropriate quality of the kava raw material (Teschke et al 2011). There may also be a pharmacogenomic component to the toxicity (Sarris et al 2011) and assessment of the causal role of kava is complicated by other factors, including concomitant drugs linked with liver toxicity, and alcohol. There is circumstantial evidence for the roles of toxic metabolites, inhibition of cyclooxygenase (COX) enzymes and depletion of liver glutathione, and pharmacogenomic effects are likely, particularly for cytochrome P450 genes. Experimental and clinical cases of hepatotoxicity show evidence of hepatitis, but the question remains whether this inflammation is caused by components of kava directly, or is due to downstream effects (Zhang et al 2011). A recent study in hepatocytes has shown that kavain has minimal cytotoxicity and methysticin moderate concentration-dependent toxicity, whereas yangonin displayed marked toxicity (Tang et al 2011).
Passion flower, Passiflora incarnata L. (Passiflorae herba) ![image](/wp-content/uploads/2017/04/B9780702033889000173_icon01-9780702033889-2.jpg)
Therapeutic uses and available evidence
Animal studies (mice, rats) have documented CNS-sedative effects or reductions in motility for aqueous ethanolic extracts of passion flower and for the constituents maltol and ethylmaltol. Anxiolytic activity has been reported in mice (Sampath et al 2010) and modulation of the GABA system is known to be involved (Appel et al 2010, Elsas et al 2010). Sedative effects are attributed at least in part to the flavonoid, particularly chrysin, content. There are few clinical studies of passiflora; however, a preliminary double-blind randomized trial using 36 patients with generalized anxiety showed the extract to be as effective as oxazepam, but with a lower incidence of impairment of job performance. It has been advocated as an adjunctive therapy for opiate withdrawal symptoms (for review, Miyasaka et al 2007). Generally, passiflora is well tolerated with few side effects; however, isolated reactions involving nausea and tachycardia in one case, and vasculitis in another, have been reported.
Valerian, Valeriana officinalis L. (Valerianae radix) ![image](/wp-content/uploads/2017/04/B9780702033889000173_icon01-9780702033889-3.jpg)
Constituents
The main components of valerian are the volatile oil and the iridoid valepotriate constituents. The volatile oil contains monoterpenes and sesquiterpenes, such as β-bisabolene, caryophyllene, valeranone, valerianol, valerenol, valerenal, valerenic acid and derivatives (Fig. 17.1). The valepotriate compounds include valtrate, didrovaltrate and isovaltrate. The valepotriates readily decompose on storage and processing to form mainly baldrinal and homobaldrinal, which are also unstable. Valerian also contains alkaloids, including valerianine and valerine, and amino acids such as arginine, γ-aminobutyric acid (GABA), glutamine and tyrosine.
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