This multicenter, randomized, case–control trial was conducted between August and October 2021 in two prominent hospitals in mainland China: the Seventh Affiliated Hospital of Southern Medical University and Anyang Traditional Chinese Medicine Hospital. A total of 136 patients participated in this trial. The study is registered with the Chinese Clinical Trial Registry (ChiCTR2100046830) and adheres to the principles of the Declaration of Helsinki and Good Clinical Practice guidelines.

Diagnostic criteria for hypertension: Following the 2018 Chinese guidelines for the management of hypertension (Writing group of 2018 Chinese guidelines for the management of hypertension, 2019), hypertension is characterized as SBP >140 mmHg and/or DBP >90 mmHg and measured on three separate clinic visits without the influence of antihypertensive medication. Patients with a documented history of hypertension currently undergoing antihypertensive therapy should be diagnosed as hypertensive, even if their blood pressure measurements fall below 140/90 mmHg. Hypertension severity is further categorized into Grades 1, 2, and 3, depending on the degree of blood pressure elevation (Table 1).

The higher grade of hypertension should be taken as the basis when systolic and diastolic blood pressure belong to different grades.

Diagnostic criteria for non-dipper blood pressure rhythms: Non-dipper blood pressure, in a narrow sense, refers to a decrease in nighttime systolic blood pressure of 0%–10%. Broadly, non-dipper blood pressure refers to all abnormal blood pressure rhythms. For the purpose of this study, we apply the broad non-dipper blood pressure rhythm criteria. The specific rhythms are defined according to the 2020 Chinese Hypertension League Guidelines on Ambulatory Blood Pressure Monitoring (Writing Group of the 2020 Chinese Hypertension League Guidelines on Ambulatory Blood Pressure Monitoring, 2021), and classified based on the percentage of nocturnal systolic blood pressure decrease (Table 2).

Inclusion criteria: (1) Male or female patients aged between 40 and 75 years of age. (2) Essential hypertension patients. (3) Non-dipper 24-hour blood pressure rhythm patients. (4) Patients maintaining a stable (longer than 1 month) regimen of Western antihypertensive medicine. (5) Patients without other complicated diseases. (6) Patients who volunteered for the trial and provided signed informed consent.

Exclusion criteria: (1) Patients known or suspected to have hypersensitivity to the test drug or any of its metabolites. (2) Patients suffering from malignant hypertension, hypertensive emergencies, hypertensive crises, or hypertensive encephalopathy. (3) Patients presenting evidence of secondary hypertension, including but not limited to conditions such as bilateral or unilateral renal artery stenosis, polycystic kidney, aldosteronism, aortic constriction, Cushing’s syndrome, or pheochromocytoma. (4) Patients with gastrointestinal lesions or gastrointestinal surgeries potentially impacting drug absorption or excretion, such as gastrointestinal resection, active gastrointestinal inflammation, ulcers, or gastrointestinal bleeding within the past 3 months. (5) Patients leading a circadian lifestyle or demonstrating irregular sleep patterns. (6) Patients with a history of alcohol or drug abuse. (7) Patients with coexisting neurological or psychiatric disorders impeding cooperation. (8) Pregnant or lactating women or those planning for childbirth in the near future. (9) Patients with severe hepatic or renal impairment (10) Patients deemed unsuitable for trial participation at the investigator’s discretion. (11) Patients who had partaken in other clinical trials within 3 months prior to the commencement of the current trial.

Withdrawal criteria: Investigator-initiated discontinuation or withdrawal criteria: Patients who experienced serious or significant adverse events, demonstrated poor compliance, or were mistakenly included and did not meet the inclusion criteria or satisfy any of the exclusion criteria were deemed unsuitable to continue the experiment.

Participant withdrawal criteria: Patients who were unwilling or unable to proceed with the clinical trial and expressed their wish to withdraw to the investigator, discontinued medication intake and testing, or became lost to follow-up, even though they did not explicitly request to withdraw from the trial, were also considered withdrawn.

A random number table method was utilized to distribute the 136 patients into the experimental and control groups at a 1:1 ratio. The random number sequence was managed by a dedicated individual within the research group, who determined the group assignment once qualified study subjects had been identified. The control group continued with their original Western antihypertensive medicine regimen, while the test group added Quanduzhong capsules, three capsules (1.48 g) twice daily, taken between 8:00–10:00 and 20:00–22:00, respectively, for a duration of 12 weeks. Quanduzhong capsules were provided free of charge by the research project team.

Quanduzhong capsules contain E. ulmoides extract and are approved by China’s Food and Drug Administration. Each 0.48 g capsule represents 2.5 g of the crude herb. Raw materials originated from Duzhong good agricultural practices (DZ GAP) bases established by Jiangxi Puzheng Pharmaceutical Co., Ltd. in Jiangxi’s Jinggangshan and Jishui regions.

For this clinical trial, capsules were manufactured by Jiangxi Puzheng Pharmaceutical Co., Ltd (Batch: batch number: 210402; Inspection: CP054210501). Processing commenced with cork removal from 2,500 g DZ. Following pulverization, 250 g of powder was reserved. The remaining material underwent milling before 85% ethanol reflux extraction (2 h). Post-filtration, ethanol recovery occurred. The resultant liquid medicine was retained. Subsequent aqueous decoction involved dual water extractions (1 h each). Combined decoctions were filtered. Filtrate integration with retained liquid preceded vacuum concentration. This yielded a paste (1.30 g/mL relative density at 80 °C). Incorporation of the reserved 250 g powder with soluble starch followed. The final steps involved drying, grinding, sieving, and encapsulation into 1,000 units. Thus, sequential extraction employed ethanol followed by water. The crude drug powder within capsules underwent innovative micropowder processing. This ensured extract homogeneity/stability while optimizing active metabolite dispersion upon administration, maximizing the therapeutic effect. Unfilled gelatin capsules came from Suzhou Capsule Co., Ltd (Batch: 12875893).

Primary efficacy indicators: Ambulatory blood pressure monitoring (ABPM). The ABPM devices employed in this study are the Beneware ABP-021 and Hingmed WBP-02A, both of which are recommended by professional societies on their website (www.stridebp.org). The primary efficacy indicators derived from these devices are as follows: recovery rate of dipper blood pressure rhythm is defined as the proportion of subjects who restored a dipper blood pressure circadian rhythm after treatment within the cohort. A dipper blood pressure rhythm is determined by the percentage decrease in nocturnal systolic blood pressure, as outlined in Table 2. Blood pressure variability index: To assess blood pressure variability, we measured the standard deviation (SD) and coefficient of variation (CV) of blood pressure fluctuations over 24 h. These metrics were calculated for overall, diurnal, and nocturnal blood pressure separately. Other efficacy indicators: Mean 24-hour blood pressure: Daytime blood pressure (dBP) is defined as the average blood pressure between 06:00 and 22:00, while nocturnal blood pressure (nBP) represents the mean between 22:00 and 06:00. Clinic blood pressure: Clinic blood pressure measurements are taken between 08:00 and 12:00. After ensuring subjects have rested for at least 5 min, investigators use an electronic sphygmomanometer (YE670C, Jiangsu Yuyue Medical Equipment) to measure blood pressure on the non-dominant arm (left arm) and record the results. Home blood pressure: Home blood pressure measurements are performed daily, at 08:00–10:00 and 20:00–22:00, using a standard electronic sphygmomanometer (YE670C, Jiangsu Yuyue Medical Equipment).

The total sample size for this study comprised 136 individuals, evenly distributed into a test group and a control group, with 68 participants in each. The primary objective of this research was to assess the recovery rate of blood pressure rhythm in both groups, both before and after treatment. Based on the preliminary examination of the participant cohort (Jiang et al., 2022), the dipper blood pressure recovery rate was observed to be 5/19 in the test group and 1/19 in the control group. Utilizing a 1:1 case ratio between the experimental and control groups, with a significance level of α = 0.05 (two-sided) and a power of β = 0.2, the required single-group sample size was calculated using PASS 11.0 software and determined to be 56 participants (N = 56). However, taking into account an anticipated dropout rate ranging from 15% to 20%, the final sample size was set at 136 individuals.

Vital signs, including heart rate, body temperature, and respiratory rate, were monitored at each visit. Laboratory indicators such as blood routine tests (red blood cells, white blood cells, platelets, hemoglobin, neutrophils), blood biochemistry indexes (creatinine, albumin, alanine aminotransferase, and aspartate aminotransferase), and urine urination routine tests (red blood cells, white blood cells, urine protein, and urobilinogen) were checked pre- and post-medication administration.

The studies involving human participants were reviewed and approved by the Ethics Committee of the Institute of Basic Theory for Chinese Medicine, China Academy of Chinese Medical Sciences (Ethical Approval Number: 2020-KY-EC-011). The patients/participants provided their written informed consent to participate in this study. The investigational product used in this trial, Quanduzhong capsules, is a marketed traditional Chinese medicine approved by the National Medical Products Administration (NMPA) of China. Prior to its initial approval, comprehensive non-clinical toxicological and safety pharmacological studies were conducted in accordance with regulatory requirements, establishing its safety profile for human use.

All research data were double-entered into the EpiData database and thoroughly tested for consistency. Statistical analysis was performed using SPSS 24.0 software. Measurement data that adhered to a normal distribution were expressed as mean ± SD, while categorical data were described as [frequency (percentage)]. A t-test was employed to compare measurement data between groups when the data conformed to a normal distribution. For data that did not conform to normal distribution, the nonparametric Wilcoxon rank-sum test was used. Ranked data were analyzed with the Cochran–Mantel–Haenszel test. All statistical tests were conducted with two-sided significance, and a P-value of less than 0.05 was considered statistically significant, indicating a difference between the groups.

Special data processing: missing data: For missing data of primary efficacy endpoints, the last observation carried forward (LOCF) method was applied for data imputation. Missing data for secondary efficacy endpoints were not carried forward. Outliers: data points determined to be outliers by investigators based on clinical judgment will be excluded after referring back to the source data to rule out data entry errors.

The chromatogram of the mixed reference substances is depicted in Figure 1. Sample solutions derived from 16 distinct batches of Quanduzhong capsules were injected to produce the fingerprint spectrum, as illustrated in Figure 1. These chromatograms were subsequently imported into the Similarity Evaluation System 2004A, operated by the National Pharmacopoeia Commission. Utilizing the peaks delineated on the reference chromatogram (Figure 2) as reference points, multi-point adjustments were executed, and the similarity was calculated. The similarity scores of the fingerprint spectrum for all 16 batches of Quanduzhong capsules were all above 0.8 (0.806, 0.818, 0.883, 0.885, 0.897 0.936, 0.906, 0.886, 0.841, 0.825, 0.820, 0.839, 0.903, 0.909, 0.898, and 0.806) (Supplementary Table S1), signifying a high degree of commonality among the peaks and a consistent quality across different batches of the medicinal material.

A total of 51 chromatographic peaks of Quanduzhong capsules were identified by LC‒MS/MS. The total ion chromatogram (TIC) and base peak chromatogram (BPC) are shown in Supplementary Figures S1,S2. Supplementary Table S2 shows the results of the chemical components in Quanduzhong capsules: they contain aucubin, chlorogenic acid, geniposide, terpineol diglucoside, and so on (Xu et al., 2023).

From 8/11/2021 to 10/2/2021, 136 participants were enrolled in the study, evenly distributed into 68 individuals in the test and control groups. Of these, 124 participants completed the study, with 61 in the test group and 63 in the control group. After thorough data cleaning and verification, the final dataset for per-protocol analysis consisted of 103 participants, comprising 52 from the test group and 51 from the control group (as depicted in Figure 3). For further details, please refer to the supplementary materials (Case shedding details).

Ultimately, the full analysis set (FAS) comprised 126 participants, with 62 individuals in the test group and 64 in the control group. The test group consisted of 28 men and 34 women, with a mean age of 60.02 ± 9.17 years, while the control group included 28 males and 36 females, with a mean age of 59.92 ± 8.83 years. For the per-protocol set (PPS), the study encompassed a total of 103 participants, with 52 individuals in the test group and 51 in the control group. The test group comprised 23 men and 29 women, having an average age of 59.79 ± 9.22 years, while the control group consisted of 22 men and 29 women, with an average age of 59.43 ± 8.77 years. There were no statistically significant differences between the two groups in either the FAS or PPS (P > 0.05). Upon comparing baseline characteristics such as weight, height, body mass index (BMI), history of smoking, drinking, drug allergies, food allergies, and other allergies, as well as hypertension grading and risk level grading, no statistically significant differences were observed between the two groups, indicating their comparability (Table 3). No significant differences in baseline were noted in the CCB and Without CCB sets (Supplementary Table S3).

No significant differences in blood pressure SD were found between the two groups in the FAS, PPS, and CCB sets (P > 0.05) (Supplementary Table S4; Table 4). In the Without CCB set, SD regulation in the test group was better than in the control group, with a statistically significant difference noted in the 24SDD (P < 0.05) (Table 4; Figure 4).

In the FAS, PPS, CCB, and Without CCB sets, no significant differences in blood pressure CV were found between the two groups (P > 0.05) (Supplementary Table S1; Table 5). However, in the Without CCB set, all CV metrics in the test group showed improvement compared to the control group (Table 5; Figure 5).

There were statistically significant differences in the recovery rate of dipper blood pressure rhythm post-medication in four sets, compared to baseline, for both the test and control groups (P < 0.05), but no statistically significant differences were observed between the two groups after treatment (Supplementary Tables S6, S7).

In the FAS and PPS, blood pressure decreased to varying degrees in both groups after treatment, and the nocturnal blood pressure exhibited a significant decline (P < 0.05). However, the difference between the test group and control group was not statistically significant (P > 0.05) (Supplementary Table S8). In the CCB set, the antihypertensive effect in the control group was significantly better than that in the test group, as were the mean value of 24-h diastolic blood pressure (24hMBP), the mean value of daytime diastolic blood pressure (dMBP), the mean value of nocturnal diastolic blood pressure (nMBP), with a statistically significant difference (P < 0.05). In the Without CCB set, the antihypertensive effect in the test group was significantly better than that in the control group, but the difference was not statistically significant (P > 0.05) (Supplementary Table S9).

There were no statistically significant differences between the text and control groups with respect to clinic blood pressure, home blood pressure, blood pressure control efficacy, and antihypertensive effect (P > 0.05).

In terms of safety parameters such as body temperature, respiration, and heart rate, no statistically significant differences were found at baseline, and after 4 weeks, 8 weeks, and 12 weeks of medication (P > 0.05). Similarly, no significant differences were noted in test indices like alanine transaminase, aspartate transaminase, and creatinine at baseline and after 12 weeks of medication (P > 0.05) (Supplementary Tables S10, S11).

Adverse event report: A total of 13 adverse events were recorded during the study period (Supplementary Table S12), including one serious adverse event (SAE): a subject experienced a sudden acute myocardial infarction, was hospitalized, and subsequently died. The subject belonged to the control group and had not taken the investigational drug; therefore, the event was determined to be unrelated to the trial medication. The remaining 12 cases were non-serious adverse events. Among these, three subjects exhibited hypotensive reactions following the administration of the investigational drug. These symptoms resolved after discontinuation of Total Eucommia Capsules, and all three subjects requested to withdraw from the clinical trial.