The Acute and Chronic Cognitive and Cerebral Blood Flow Effects of a Sideritis scardica (Greek Mountain Tea) Extract: A Double Blind, Randomized, Placebo Controlled, Parallel Groups Study in Healthy Humans.

BACKGROUND: The presence of polyphenols such as hydroxy-cinnamic acids and flavonoids in Sideritis scardica (Greek mountain tea) are likely responsible for the cognitive and mood effects of its consumption and this could be underpinned by the ability of such polyphenols to prevent monoamine neurotransmitter reuptake and to increase cerebral blood flow (CBF). OBJECTIVE: The current study extends the small amount of Sideritis scardica literature in humans by assessing both cognitive and mood outcomes in a sample of older adults, as well as blood pressure (BP) and CBF, in a subsample, utilizing near-infrared spectroscopy (NIRS). DESIGN: This randomized, double-blind, placebo-controlled, parallel groups trial randomized N = 155, 50⁻70-year-old male and female participants who were assessed for the cognitive (N = 140), mood (N = 142), BP (N = 133) and CBF (N = 57) effects of two doses of Greek mountain tea (475 and 950 mg) as well as an active control of 240 mg Ginkgo biloba, and a placebo control, following acute consumption (Day 1) and following a month-long consumption period (Day 28). RESULTS: Relative to the placebo control, 950 mg Greek mountain tea evinced significantly fewer false alarms on the Rapid Visual Information Processing (RVIP) task on Day 28 and significantly reduced state anxiety following 28 days consumption (relative also to the active, Ginkgo control). This higher dose of Greek mountain tea also attenuated a reduction in accuracy on the picture recognition task, on Day 1 and Day 28, relative to Ginkgo and both doses of Greek mountain tea trended towards significantly faster speed of attention on both days, relative to Ginkgo. Both doses of Greek mountain tea, relative to placebo, increased oxygenated haemoglobin (HbO) and oxygen saturation (Ox%) in the prefrontal cortex during completion of cognitively demanding tasks on Day 1. The higher dose also evinced greater levels of total (THb) and deoxygenated (Hb) haemoglobin on Day 1 but no additional effects were seen on CBF on Day 28 following either dose of Greek mountain tea. Ginkgo biloba led to lower levels of Ox% and higher levels of Hb on Day 1 and lower levels of both HbO and THb on Day 28. CONCLUSIONS: The significantly improved cognitive performance following Greek mountain tea on Day 1 could be due to significant modulation of the CBF response. However, these improvements on Day 28 are more likely to be due to the reductions in state anxiety and, taken together, suggests that the former mechanism is more likely to facilitate acute cognitive effects and the latter more likely to underpin more prolonged cognitive improvements.

Comparative evaluation of two different Artemisia dracunculus L. cultivars for blood sugar lowering effects in rats.

Recent concerns about the potential carcinogenicity of estragole and methyleugenol led a number of regulatory bodies to call for restrictions on the use of herbs that contain these constituents. A number of medicinal plants produce essential oils that contain estragole and methyleugenol, including Artemisia dracunculus L. (tarragon). Previous studies have proven the antidiabetic properties of tarragon. In order to address the safety concerns of estragole containing tarragon extracts, an extraction procedure was developed to minimize the estragole and methyleugenol content in tarragon extracts and the ethanol versus aqueous extracts from two Artemisia dracunculus cultivars (French and Russian tarragon) were tested for blood glucose lowering effects in rats. It could be demonstrated that aqueous extracts of both Artemisia cultivars did not contain detectable amounts of estragole and methyleugenol, whereas ethanol extracts (60% v/v) of the French cultivar contained higher levels of the aforementioned compounds than those of the Russian cultivar. Further testing revealed that Russian tarragon lowered blood glucose levels in rats after glucose challenge, with the ethanol extract being as active as the aqueous extract. The results suggest that by using adequate production procedures the amount of potentially harmful compounds in extracts can be limited without affecting the overall pharmacological activities of these preparations.

Artemisia dracunculus L. (tarragon): a critical review of its traditional use, chemical composition, pharmacology, and safety.

Artemisia dracunculus L. (tarragon) has a long history of use as a spice and remedy. Two well-described "cultivars" (Russian and French) are used widely and differ in ploidy level, morphology, and chemistry. Key biologically active secondary metabolites are essential oils (0.15-3.1%), coumarins (>1%), flavonoids, and phenolcarbonic acids. In vivo studies mainly in rodents, particularly from Russian sources, highlight potential anti-inflammatory, hepatoprotective, and antihyperglycemic effects. Despite concerns about the toxic effects of two of its main constituents, estragole (up to 82%) and methyleugenol (up to 39%), no acute toxicity or mutagenic activity has been reported at doses relevant for human consumption. Water extracts of A. dracunculus contain very low amounts of estragole and methyleugenol and, therefore, are considered to pose a very limited risk. Overall, a stronger focus on clinical studies and precise taxonomic and phytochemical definition of the source material will be essential for future research efforts.

Comparative evaluation of two different Opuntia ficus-indica extracts for blood sugar lowering effects in rats.

Stems of Opuntia ficus-indica (L.) Mill. (OFI) are traditionally used in Mexico to treat diabetes mellitus. Less research data are available for combinations of stem and fruit preparations. The present study was designed to investigate the effects of an aqueous extract prepared from the cladodes and a proprietary stem/fruit skin-blend (stem/fruit skin ratio 75/25) of OFI on blood glucose and plasma insulin in normal rats. A dose finding study with the traditional cladode OFI extract revealed that maximum effects on blood glucose and insulin were observed after oral administration in a dose range of 6-176 mg/kg. The proprietary OFI blend significantly lowered blood glucose levels in the glucose tolerance test to a similar extent (p < 0.05 vs control) as the traditional aqueous cladode extract when administered in a dose of 6 mg/kg. In contrast to the aqueous extract, the proprietary blend significantly increased basal plasma insulin levels (p < 0.01 vs control) indicating a direct action on pancreatic beta cells. The results suggest that both OFI extracts exert hypoglycemic activities in rats in doses as low as 6 mg/kg but that the effects of the proprietary stem/fruit blend were more pronounced in our model.

Flavonoids of Cynara scolymus possess potent xanthinoxidase inhibitory activity in vitro but are devoid of hypouricemic effects in rats after oral application.

Artichoke (Cynara scolymus L.) leaves have been historically used for the treatment of hyperuricemia and gout, however whether artichoke is truly efficacious for this indication, is still a matter of debate. Thus, the goal of the present study was first to examine the xanthine oxidase (XO) inhibitory activity of an artichoke leaf extract (ALE) and some of its main compounds in vitro and then further test potentially active substances for possible hypouricemic effects using an in vivo rat model. The in vitro study showed that ALE inhibited XO with only minimal inhibitory action (< 5 %) at 100 microg/mL. However, when selected compounds were tested, the caffeic acid derivatives revealed a weak XO inhibitory effect with IC (50) > 100 microM. From the tested flavones the aglycone luteolin potently inhibited XO with an IC (50) value of 1.49 microM. Luteolin 7-O-glucoside and luteolin 7-O-glucuronide showed lower XO inhibition activities with IC (50) values of 19.90 microM and 20.24 microM, respectively. However, oral administration of an aqueous ALE, luteolin, and luteolin 7-O-glucoside did not produce any observable hypouricemic effects after acute oral treatment in potassium oxonate-treated rats. After intraperitoneal injection of luteolin a decrease in uric acid levels was detected suggesting that the hypouricemic effects of luteolin are due to its original form rather than its metabolites produced by the gut flora. In conclusion, an aqueous ALE, caffeic acid derivatives and flavones exerted XO inhibitory effects in vitro but a hypouricemic activity could not be confirmed after oral administration.