THE STUDY OF THE MECHANISM OF ACTION OF CUCUMBER FRUIT (CUCUMIS SATIVUS L.) IN LOWERING BLOOD PRESSURE AND ITS IMPACT ON THE EFFECTIVENESS OF ANTIHYPERTENSIVE DRUGS

• Main Author: Hendrayana, Tomi
• Format: Dissertations
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/87181
• Institution: Institut Teknologi Bandung

Hypertension is one of the degenerative diseases that affects around 30.8% of the Indonesian population, and makes it the highest risk factor for cardiovascular disease, which is the leading cause of death. According to the results of the health survey in 2023 (Survey Kesehatan Indonesia / SKI 2023), 53.3% of hypertension patients in Indonesia were not compliant in taking antihypertensive medication for various reasons, one of which is the use of traditional medicine. With the advancement of technology, the policies of the Indonesia Ministry of Health, and increasing public awareness of health, many medicinal plants are being utilized as alternative or adjuvant therapies alongside standard treatments. One traditional plant commonly used by Indonesians for lowering blood pressure is cucumber (Cucumis sativus L.). However, studies on the antihypertensive activity of cucumber and its interactions with standard antihypertensive drugs have not been extensively conducted. This study aims to investigate the pharmacological activity, the mechanism of action of cucumber in lowering blood pressure, and the potential interactions between cucumber and standard drugs used for hypertension therapy. The research stages include the collection of samples, plant determination to ensure that the material used is cucumber, and production a concentrated cucumber extract. This concentrate is then subjected to quality characterization of the extract, phytochemical screening, and element analysis. Subsequently, various tests are conducted to evaluate the antihypertensive effects as well as diuretic-saluretic effects. In these tests, four doses are used such as 9, 18, 27, and 36 g/kg body weight of rats, which correspond to human consumption of 100, 200, 300, and 400 mg or approximately 1–4 cucumbers, respectively. Additionally, a pharmacodynamic interaction study is performed by administering a combination solution of cucumber extract at specific doses with standard drugs to the test animals. Based on the results, the most dominant mechanism of action in reducing blood pressure is determined, followed by pharmacokinetic interaction tests to assess the impact of cucumber extract administration on the pharmacokinetic parameters of standard antihypertensive drugs. Finally, an in silico molecular docking simulation is conducted to identify potential compounds in cucumber responsible for lowering blood pressure. Elemental analysis of cucumber extract using the atomic absorption spectrophotometry (AAS) method revealed that each gram of the sample contains: glucose 88,829.9 µg; calcium 16.60 µg; sodium 490.77 µg; potassium 20,118.11 µg; iron 19.57 µg; and zinc 3.25 µg. The first antihypertensive test conducted was measuring cucumber extract's activity in lowering blood pressure through the inhibition of ACE (in-vitro test). This test utilized Hip-His-Leu as a substrate, and the product formed from the reaction between the enzyme and the substrate was measured using a UV-Vis spectrophotometer at a wavelength of 228 nm. Based on the absorbance values obtained, the percentage of inhibition was calculated and expressed as IC50. Cucumber extract 100 µg/mL demonstrated an ACE inhibition of 56.45 ± 3.49%, classified as a moderate ACE inhibitor. The IC50 value of cucumber extract was 86.65 µg/mL, whereas captopril was 2.40 µg/mL. In the diuretic and saluretic effects testing, cucumber extract was administered in varying doses of 9, 18, 27, and 36 g/kg, using the modified Lipschitz method. The standard comparator drug used was furosemide 3.6 mg/kg. Urine volume collected during the 24-hour observation period for the normal control group and the test groups administered cucumber at doses of 9, 18, 27, and 36 g/kg were 8.58; 10.10; 10.31; 13.45; and 13.47 mL, respectively. The Na+/K+ levels detected for each group were 2,812/4,691; 3,200/5,712; 3,562/5,721; 3,704/6,011; and 4,207/6,039 ppm, respectively. The results indicated that cucumber extract at doses of 27 and 36 g/kg exhibited diuretic activity, while saluretic effects were observed starting from 9 g/kg dose. The strength of diuretic and saluretic effects increased proportionally with the doses of cucumber extract. However, these effects were still lower compared to those of furosemide. Another antihypertensive test was conducted using a hypertensive animal model induced by dexamethasone. The dosage scheme was the same as the previous tests, with cucumber extract doses of 9, 18, 27, and 36 g/kg, and amlodipine was used as a standard antihypertensive comparator. Blood pressure in rats was measured using a non-invasive method (CODA® tail-cuff blood pressure system). The hypertensive animal model was established after 10 days of continuous dexamethasone induction. Cucumber extract exhibited antihypertensive effects, as evidenced by the data on day 17 (7 days of test treatment). The average reduction in systolic blood pressure in the groups receiving C. sativus at doses of 9, 18, 27, and 36 g/kg was 20.7; 20.1; 21.0; and 28.8 mmHg, respectively. Corresponding reductions in diastolic blood pressure were 12.9; 18.2; 17.5; and 19.6 mmHg, respectively. The antihypertensive effect of cucumber extract increased proportionally with higher doses but remained lower compared to amlodipine. The other model investigated in this study used hypertensive rats model induced by adrenaline, and propranolol as the standard antihypertensive comparator. Over 28 days, animals were administered the test solution (cucumber at various doses or propranolol). On the 28th day, 30 minutes after administering the test solution, an adrenaline injection was injected, and blood pressure was measured at 0, 15, 30, 60, 90, and 120 minutes post-injection. Cucumber extract demonstrated antihypertensive effects, as shown by the data at 30 minutes after adrenaline induction. The average differences in systolic blood pressure increased from baseline for the groups receiving C. sativus at doses of 9, 18, 27, and 36 g/kg were 28.55; 24.28; 21.93; and 18.31 mmHg, respectively. The corresponding differences in diastolic blood pressure increased were 19.97; 14.07; 12.09; and 11.17 mmHg, respectively. Blood pressure increases in the test groups were significantly lower than those in the positive control group (adrenaline-induced animals without the test preparation), and this difference was statistically significant. The antihypertensive activity of cucumber extract increased with higher doses; however, its ability to inhibit blood pressure elevation remained lower compared to propranolol. The final test involved a hypertensive animal model induced by angiotensin II, with losartan used as the standard drug. The results showed that cucumber extract had antihypertensive effects, with its potency increasing proportionally with the dose. At 30 minutes after angiotensin II induction, the average differences in systolic blood pressure increases from baseline for groups treated with C. sativus extract at doses of 9, 18, 27, and 36 g/kg were 28.75; 24.75; 22.75; and 11.50 mmHg, respectively. The corresponding differences in diastolic blood pressure increases were 18.25; 15.75; 15.50; and 9.00 mmHg, respectively. Higher doses of cucumber extract demonstrated stronger inhibition of blood pressure increases induced by angiotensin II. Notably, the antihypertensive effect of cucumber extract at a dose of 36 g/kg was comparable to that of losartan at 4.5 mg/kg. For the combination testing of cucumber extract with standard antihypertensive drugs, it was found the combination of cucumber extract with furosemide exhibited an additive effect for diuretic activity and a synergistic effect for saluretic activity. For combinations with amlodipine or propranolol, the nature of the combination could not be conclusively evaluated. The combination of cucumber extract with losartan displayed an additive effect. From all the experiments conducted, it was proven that cucumber extract exhibits antihypertensive effects through multiple mechanisms, including ACE inhibitory, diuretic-saluretic activities, adrenergic receptor blockade, and angiotensin receptor blockade (ARB). The most dominant mechanism of action was identified as the blockade of angiotensin receptors activity. The antihypertensive activity of cucumber extract was observed starting at a dose of 9 g/kg, equivalent to the consumption of 100 g or about 1 cucumber for humans. In the study using dexamethasone as the inducer for increasing blood pressure, all test animal groups showed a reduction in systolic blood pressure greater than 20 mmHg and diastolic blood pressure more than 10 mmHg. The strength of cucumber extract in lowering blood pressure increased proportionally with the dose. The inhibition of blood pressure elevation induced by angiotensin II was observed to be weaker for the cucumber extract at a dose of 36 g/kg compared to losartan at 4.5 mg/kg. However, the difference was not statistically significant, indicating that the effects were comparable. These data provide preliminary scientific evidence to explore the potential of cucumber as an antihypertensive agent. To confirm the results of the combination test between cucumber extract and losartan, which exhibited an additive effect, a pharmacokinetic study was conducted. The results indicated that cucumber extract could influence the pharmacokinetic parameters of losartan, leading to an increase in Cmax, AUC0-t, and T1/2 elimination. Additionally, there was a shift in Tmax, along with a decrease in clearance (CL) and volume of distribution (Vd). These changes suggest that cucumber extract interacts with losartan, potentially altering its absorption, distribution, and elimination profiles. In the in silico testing, it was found that compounds in cucumber, including cucumerin A, isorhamnetin, cucumegastigmane, cucurbitacin C, and cucurbitacin A, were suspected to have some similarity to lisinopril and are proposed to be responsible for exerting antihypertensive effects through the ACE inhibitor (ACEI) pathway. These compounds appear to interact with the ACE enzyme in a similar manner to lisinopril, suggesting a potential mechanism of action for the antihypertensive effects of cucumber extract.