The dose effect of sarmentosin on platelet MAO-B activity in healthy adult males

This study will investigate the effect of a sarmentosin-enriched blackcurrant extract and its effect on MAO-B inhibition. The extract is a freeze-dried powder that will be reconstituted in 250 mL water and served in sealed drink bottles. We will implement an unblinded, dose-escalation, placebo-controlled, repeated measures designed. Prospective participants who have passed the study’s the study’s inclusion/exclusion criteria will be asked to attend a familiarisation where they will meet with the study’s principal investigator or trial coordinator. During this session , the study’s trial coordinator (Research Associate, approx. 8 years experience in human dietary intervention studies) or the principal investigator (Research Scientist, PhD) will explain the logistics of the trial to them and answer any questions they may have. Enrolled participants (n = 15) will attend a maximum of nine trial days. Participants will be given a list of foods (e.g. blackcurrant and blackcurrant-containing supplements) to abstain from consuming 18 hours prior each trial day. Participants will be also be asked to refrain from eating any food or drink (other than water) 10 h before the start of their scheduled trial day. Upon arriving at the research facility, complete a brief questionnaire confirming compliance with the fasting and dietary restrictions. Participants will then complete a mood questionnaire, then a venous blood sample (approximately 20 mL) will be collected from them. They will then be given a single serve of their allocated intervention (sarmentosin drink or placebo) to consume as quickly as they can. Participants will remain in the facility for a 2-hour observation period during which they will continue fasting, except for water provided to them. After 2 hours, participants will be asked to complete the same mood questionnaire they completed when they first arrived, then a second 20 mL venous blood sample will be collected. After at least three days following their trial day, participants will return to receive the next higher dose of sarmentosin compared to their previous session. This process will continue until all interventions (placebo and up to eight escalating sarmentosin doses) have been completed, with venous blood collections following the same schedule on each trial day. This is a dose-escalation study in which participants will be asked to consume a placebo (0 mg sarmentosin) on their first trial day, followed by escalating doses of sarmentosin ( 2.5, 5, 10, 20, 30, and 40 mg) on subsequent trial days. If the dose–response curve does not clearly identify the concentration of sarmentosin required to inhibit 50% of MAO-B activity, participants will be asked to return for two additional trial days. On these days, they will receive sarmentosin doses within the 2.5–40 mg range, selected based on the preliminary dose–response data from the initial six doses.