Xiang Mao

Healthy volunteers took a lemongrass leaf infusion (the Brazilian abafado) as a single dose and daily for two weeks. There were no changes in glucose, urea, creatinine, cholesterol, triglycerides, bilirubin, transaminases, alkaline phosphatase, protein, LDH or CPK, and no abnormality on urinalysis, EEG or ECG; slight rises in direct bilirubin and amylase occurred without clinical signs. In a double-blind arm, 50 volunteers showed no difference from placebo in sleep induction, sleep quality, dream recall or reawakening, and 18 high trait-anxiety subjects showed no anxiolytic effect. The authors concluded the tea is atoxic in short-term use but lacks the hypnotic and anxiolytic properties popularly attributed to it. Note that this two-week study does not address the renal changes later found at 30 days.

105 adults aged 18 to 35 were randomised to daily infusions prepared from 2, 4 or 8 g of Cymbopogon citratus leaf powder for 30 days. Creatinine clearance and estimated glomerular filtration rate fell significantly by day 30 in men and women at every dose, and by day 10 in women at 8 g. Serum and urinary creatinine rose in all groups, and serum urea rose at 4 and 8 g. At day 10 the lower doses showed increased urine volume, urination frequency and saliuretic indices without a filtration change. The authors describe dose- and time-dependent adverse effects on renal function. This is the most clinically consequential human finding for the herb and is the basis for limiting duration of use.

90 HIV-positive patients with oral thrush at a South African hospice were randomised to 0.5 percent aqueous gentian violet, lemon juice or a Cymbopogon citratus infusion for 11 days; 83 completed. On intention-to-treat analysis no comparison reached significance, so the trial did not demonstrate superiority for the lemongrass infusion. In the completers analysis lemon juice outperformed gentian violet. The honest reading is that lemongrass infusion was not shown to beat standard treatment, and the trial is small and open.

40 healthy male volunteers inhaled lemongrass essential oil (three or six drops), tea tree oil as an aroma control, or distilled water, then performed a video-monitored Stroop Colour-Word Test. Both lemongrass doses reduced state anxiety and subjective tension immediately after inhalation and allowed complete recovery within five minutes of the stressor, unlike controls. Physiological measures, heart rate and gastrocnemius EMG, were not altered by any treatment, as is also the case with diazepam in this model. The effect is subjective, brief and olfactory; the study does not support an oral anxiolytic claim.

22 hypercholesterolaemic subjects (mean 315 mg/dL) took a daily capsule of 140 mg lemongrass oil for 90 days. The overall paired difference only approached significance (p less than 0.06). Subjects split into 14 non-responders, whose cholesterol was unchanged, and 8 responders, who fell 25, 33 and 38 mg/dL at 30, 60 and 90 days. The effect was not sustained 90 days after stopping. This is a small uncontrolled study with a post hoc responder split and should be read as hypothesis-generating, not as evidence that lemongrass lowers cholesterol.

Lemongrass essential oil (geranial 39.9 percent, neral 27.4 percent) reduced contraction amplitude and spontaneous rate in isolated guinea pig atria with IC50 values of 106.8 and 258.4 micrograms/mL, and induced spontaneous contractions, that is it was arrhythmogenic. In an ouabain arrhythmia model it shortened the time to arrhythmia onset by 67.8 percent. Patch clamp showed concentration- and voltage-dependent reduction of the cardiac sodium current in Nav1.5-expressing HEK293 cells and of the L-type calcium current in ventricular myocytes. This is the key safety study for concentrated oral or high-dose essential oil use.

Searched four databases and included 10 in vivo and in vitro studies of Cymbopogon citratus against oral candidiasis, assessing quality with ROBINS-I. The authors concluded that antifungal activity is potent in laboratory work but that the clinical evidence is limited and that trials are needed before clinical use can be recommended. The title of this review is itself an example of the naming problem this database exists to avoid: lemon verbena is Aloysia citrodora, a Verbenaceae shrub, and is not Cymbopogon citratus, a Poaceae grass. The review's content concerns Cymbopogon citratus.