A growing body of evidence demonstrates the efficacy of Garcinia cambogia-derived natural (–)-hydroxycitric acid (HCA) in weight management by curbing appetite and inhibiting body fat biosynthesis. However, the exact mechanism of action of this novel phytopharmaceutical has yet to be fully understood. In a previous study, we showed that in the rat brain cortex a novel HCA extract (HCA-SX, Super CitriMax™) increases the release/availability of radiolabeled 5-hydroxytryptamine or serotonin ([3H]-5-HT), a neurotransmitter implicated in the regulation of eating behavior and appetite control. The aim of the present study was 2-fold: (a) to determine the effect of HCA-SX on 5-HT uptake in rat brain cortex in vitro; and (b) to evaluate the safety of HCA-SX in vivo. Isolated rat brain cortex slices were incubated in oxygenated Krebs solution for 20 min and transferred to buffer solutions containing [3H]-5-HT for different time intervals. In some experiments, tissues were exposed to HCA-SX (10 μM – 1 mM) and the serotonin receptor reuptake inhibitors (SRRI) fluoxetine (100 μM) plus clomipramine (10 μM). Uptake of [3H]-5-HT was expressed as d.p.m./mg wet weight. A time-dependent uptake of [3H]-5-HT occurred in cortical slices reaching a maximum at 60 min. HCA-SX, and fluoxetine plus clomipramine inhibited the time-dependent uptake of [3H]-5-HT. At 90 min, HCA-SX (300 μM) caused a 20% decrease, whereas fluoxetine plus clomipramine inhibited [3H]-5-HT uptake by 30%. In safety studies, acute oral toxicity, acute dermal toxicity, primary dermal irritation and primary eye irritation, were conducted in animals using various doses of HCA-SX. Results indicate that the LD50 of HCA-SX is greater than 5000 mg/kg when administered once orally via gastric intubation to fasted male and female Albino rats. No gross toxicological findings were observed under the experimental conditions. Taken together, these in vivo toxicological studies demonstrate that HCA-SX is a safe, natural supplement under the conditions it was tested. Furthermore, HCA-SX can inhibit [3H]-5-HT uptake (and also increase 5-HT availability) in isolated rat brain cortical slices in a manner similar to that of SRRIs, and thus may prove beneficial in controlling appetite, as well as treatment of depression, insomnia, migraine headaches and other serotonin-deficient conditions.