Platelet inhibitory effects of juices from Pachyrhizus erosus L. root and Psidium guajava L. fruit: a randomized controlled trial in healthy volunteers

Abstract

Background: The purpose of this study is to investigate cardiovascular benefits of juices obtained from two commonly consumed fruits in Thailand, Pachyrhizus erosus, L. (yam bean) and Psidium guajava, L. (guava), by examining their acute cardiovascular effects in healthy volunteers. Possible involvements of the dietary nitrate on their effects were investigated as well.

Method: Thirty healthy volunteers were randomly divided into three groups of 10 subjects per group and each group was allocated to drink 500 ml of freshly prepared yam bean root juice, guava fruit juice, or water. Systemic nitrate and nitrite concentrations, heart rate, systolic and diastolic blood pressure, serum K(+) concentrations, ex vivo platelet aggregation, and plasma cGMP concentrations were monitored at the baseline and at various time points after the intake of juices or water. Data were compared by repeated measures ANOVA.

Results: Following the ingestion of both yam bean root juice and guava fruit juice, collagen-induced but not ADP-induced platelet aggregation was attenuated. Ingestion of yam bean root juice increased systemic nitrate and nitrite concentrations whereby elevated nitrite concentrations correlated with the extent of inhibiting collagen-induced platelet aggregation. In addition, positive correlation between systemic nitrite and plasma cGMP concentrations and negative correlation between plasma cGMP concentrations and the extent of collagen-induced platelet aggregation were revealed. Nevertheless, yam bean root juice reduced only diastolic blood pressure while guava fruit juice reduced heart rate, systolic and diastolic blood pressure.

Conclusion: The present study has illustrated, for the first time, acute inhibitory effects of yam bean root juice and guava fruit juice on ex vivo collagen-induced platelet aggregation in healthy subjects. Dietary nitrate was shown to underlie the effect of yam bean root juice but not that of guava fruit juice. Following yam bean root juice ingestion, systemic nitrate apparently converts to nitrite and further to NO which may attenuate platelet responses to collagen stimulation. Cardiovascular benefits of juices from yam bean root and guava fruit are noteworthy in term of the cardiovascular health-promoting approach.

Trial registration: Randomized controlled trial TCTR20150228001 .

Keywords: Antiplatelet effect; Blood pressure lowering effect; Guava fruit juice; Plasma cGMP; Systemic nitrate; Systemic nitrite; Yam bean root juice.

Fig. 1

The flow diagram of progress through phases of the study. Legend: Data monitoring at the baseline was performed prior to the water or juice ingestion. (BP: blood pressure, HR: heart rate, YBR: yam bean root, GF: guava fruit)

Fig. 2

Time-plasma concentration profiles of nitrate and nitrite. Legend: Plasma nitrate (a) and plasma nitrite (b) concentrations in healthy volunteers at various time points after the ingestion of water, YBR juice, or GF juice. Data are expressed as mean ± SEM from 10 subjects in each group. ^a P < 0.05 Dunnett’s posttest compared to the baseline, ^b P < 0.05 Bonferroni posttest vs. the control

Fig. 3

Effects of the juice ingestion on ex vivo ADP-induced platelet aggregation. Legend: Ex vivo ADP-induced platelet aggregation after the ingestion of water (a), YBR juice (b), or GF juice (c). Data are expressed as mean ± SEM from 10 subjects in each group. ^a P < 0.05 Dunnett’s posttest compared to the baseline

Fig. 4

Effects of the juice ingestion on ex vivo collagen-induced platelet aggregation. Legend: Ex vivo collagen-induced platelet aggregation after the ingestion of water (a), YBR juice (b), or GF juice (c). Data are expressed as mean ± SEM from 10 subjects in each group. ^a P < 0.05 Dunnett’s posttest compared to the baseline

Fig. 5

Effects of the juice ingestion on plasma cGMP concentrations. Legend: Plasma cGMP concentrations at three time points – baseline, 2.5 and 5 h after the ingestion of water, YBR juice, or GF juice. Data are expressed as mean ± SEM from 10 subjects in each group. ^a P < 0.05 Dunnett’s posttest compared to the baseline, ^b P < 0.05 Bonferroni posttest vs. the control

Fig. 6

The association between plasma cGMP and plasma nitrite concentrations. Legend: A positive correlation between the change of plasma cGMP concentrations vs. the change of circulating nitrite concentrations in healthy volunteers following YBR juice ingestion (n = 10)

Fig. 7

The association between plasma cGMP concentrations and collagen-induced platelet aggregation. Legend: The negative correlation between plasma cGMP concentrations and the maximal extent of platelet aggregation (% Light transmission) induced by (a) 0.5 μg/ml collagen (b) 1 μg/ml collagen and (c) 2 μg/ml of collagen in YBR juice ingested volunteers (n = 10)

Fig. 8

Acute cardiovascular changes after the juice ingestion. Legend: Effects of YBR juice ingestion on - SBP (a), DBP (c) and HR (e); effects of GF juice ingestion on - SBP (b), DBP (d) and HR (f) as compared to the control. Data are expressed as mean ± SEM from 10 subjects in each group. ^a P < 0.05 Dunnett’s posttest compared to the baseline, ^b P < 0.05 Bonferroni posttest vs. the control