Chemical profiles of the active fraction from Prinsepia utilis Royle leaves and its anti-benign prostatic hyperplasia evaluation in animal models

Background The Prinsepia utilis Royle leaves (P. utilis) is a folk herb used for benign prostatic hyperplasia (BPH) control by ethnic minorities for centuries in China with rich in resources. Our previous studies have confirmed the anti-BPH effect of its water extract (QCJ) and the active fraction (Fr. B) separated from the QCJ by animal test. The Fr. B from P. utilis should be a potential candidate for BPH control. Methods In this study, the chemical ingredients of Fr. B were identified by UPLC-QTOF-MS, and quantified by HPLC. Murine animal models were divided into 8 groups, Sham rats, BPH rats, BPH rats administered with finasteride (1 mg/kg), BPH rats administered with Pule’an (460 mg/kg), BPH rats administered with low, high dosage of QCJ (860 mg/kg, 2580 mg/kg respectively), BPH rats administered with low, high dosage of Fr. B (160 mg/kg, 480 mg/kg respectively). The expression of vascular endothelial growth factor (VEGF) in the prostate tissue of rats was tested, and serum levels of dihydrotestosterone (DHT), testosterone (T), estradiol (E2), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α) and total superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT), malondialdehyde (MDA) in prostate homogenate were measured. One-way ANOVA followed by LSD was used for statistical analysis. Results The BPH rats treated by Fr. B exhibited significant reductions of VEGF and MDA levels, as well as significant increases of SOD, GSH-Px and CAT in the prostate tissue after 28 day administration (P < 0.05). Moreover, Fr. B significantly reduced DHT, DHT/E2 ratio, TNF-α, while increased T levels in serum of BPH rats (P < 0.05). UPLC-QTOF-MS analysis revealed 10 flavonoids as the key constituents of this fraction, which accounted for 54.96% of all substance of Fr. B. The relative contents of compound 1, 2 are 11.1%, 13% in Fr. B respectively. Conclusions These results indicated that the Fr. B obtained from P. utilis alleviated the symptoms of BPH rats through multiple mechanisms including reduction of DHT/E2 ratio, inhibition of growth factor, anti-inflammation and anti-oxidation, in which flavonoids might be the key constituents. It supported the hypothesis that the Fr. B should be further explored as a candidate for BPH patients.

fruits are traditionally used to treat toothache, carbuncle and gangrene [1]. Pharmacological studies showed that the stems and leaves of P. utilis had the functions of anti-osteoporosis [2], regulating blood lipids [3], antitumor [4], anti-oxidation [2], anti-inflammation [5], antibacteria [6], etc. Interestingly, as a multi-ethnic herb, the leaves of P. utilis is used as tea in folk for benign prostatic hyperplasia (BPH) symptom control by Naxi, Bai, Yi, Mosuo and other ethnic minorities for centuries in Yunan province.
Generally, BPH is considered to be a product of androgen action upon an aging prostate. But longitudinal epidemiological studies showed that androgen levels were unlikely to be solely responsible [7]. There are many potential etiological factors contributing to BPH pathogenesis such as inflammation, oxidative stress, imbalance between prostate cell growth and apoptosis [8,9]. Our previous studies confirmed the anti-BPH activities of P. utilis leaves extract (QCJ) on BPH rats and the Fr. B separated from QCJ as the active fraction [10]. However, whether its anti-BPH activity is related to anti-inflammation, anti-oxidation or anti-androgenic need further study.
According to the chemical reports on P. utilis, flavonoids, amino acids, steroids and terpenoids have been isolated from P. utilis fruit, stems and leaves [11]. The content of total flavonoids is up to be 7.25% in P. utilis fruit [12], 3% in stems and leaves of P. utilis [13]. The flavonoids usually exhibited potent anti-inflammatory and antioxidant properties. It was reported that flavonoid-rich fraction from P. utilis fruits exhibited strong radical scavenging activities [14]. Many medicinal plants rich in flavonoids showed well anti-BPH potential [15,16], which were reported to exert BPH protective effect through regulating inflammatory responses and reducing oxidative stress.
Therefore, these findings led us to further analyze the chemical ingredients of Fr. B with UPLC-QTOF-MS, assess its therapeutic effects on testosterone-induced BPH rats by oral administration of Fr. B and compared with finasteride and Pule'an used as first-line therapy in China in terms of its efficacy and possible mechanisms as anti-androgenic, anti-oxidant and anti-inflammatory in this study.

Materials and methods
Extraction and isolation of Fr. B P. utilis leaves was collected from Dali, Yunnan, China and authenticated by one of the authors Xiaobo Li. Voucher specimen has been deposited at herbarium of School of Pharmacy, Shanghai Jiao Tong University, Shanghai, China. Preparation of Fr. B was previously described by Wu et al [10]. Dried and powdered leaves (2 kg) were re-fluxed 3 times with distilled water. The combined extraction was filtrated and then concentrated under reduced pressure to obtain a crude aqueous extract (QCJ). The sample was redissolved, and then separated by macroporous resin AB-8. After adsorption, the resin was washed with 5% ethanol without collection, followed by 40% ethanol, the elution was then evaporated under vacuum at 65 °C and lyophilized to obtain Fr. B.

Animals and BPH models
Male Spraue-Dawley rats (180-220 g) were procured from Shanghai Slac Laboratory Animal Co. Ltd. (Shanghai, China), and housed in the Laboratory Animal Center of Shanghai Jiao Tong University (Shanghai, China). The animals were housed in groups under controlled room temperature (25 ± 2 °C, 55 ± 10% relative humidity) with a 12/12 h light/dark cycle. Standard laboratory chow and water were available ad libitum. All experimental procedures were approved by the Animal Ethics Committee of Shanghai Jiao Tong University (Shanghai, China). All methods are reported in accordance with ARRIVE guidelines (https:// arriv eguid elines. org) for the reporting of animal experiments.
Following 1 week acclimation, rats were randomly assigned to 8 groups (n = 10) as following, Sham, BPH model, Finasteride, Pule'an, Low QCJ, High QCJ, Low Fr. B, High Fr. B. The scrotum of the sham animals were cut following sewing up without cutting off the both testicles. Rats in the other groups were castrated. After incision disinfection with penicillin for 1 week, sham rats were treated with saline (s.c., 0.5 ml/kg, alternate days) and 0.5% CMC-Na (i.g. 10 ml/kg, daily). BPH group rats were received testosterone propionate (s.c., 10 mg/kg) alternate days and 0.5% CMC-Na (i.g. 10 ml/kg) daily for 4 weeks [17,18]. Two positive groups, the rats were treated with testosterone propionate (s.c., 10 mg/kg) and received a treatment with finasteride (i.g., 1 mg/kg) or Pule'an (i.g., 460 mg/kg). Low/High QCJ group rats were treated with testosterone propionate (s.c., 10 mg/ kg) and received a treatment with QCJ (i.g., 860 mg/kg or 2580 mg/kg respectively). Low/High Fr. B group rats were treated with testosterone propionate (s.c., 10 mg/kg) and received a treatment with Fr. B (i.g., 160 mg/kg or 480 mg/ kg respectively). Low dosage of QCJ or Fr. B was clinically equivalent doses (1.8 g Crude drug/kg). High dosage of QCJ or Fr. B was three times the clinical equivalent doses (5.4 g Crude drug/kg).
At the end of experiment, animals were sacrificed under anaesthesia after blood sample collection. The prostates were removed and ventral prostate tissues were fixed in 10% neutral buffered formalin and embedded in paraffin for both histological and immunohistochemical examinations. The remainder of each prostate was stored at − 80 °C and used for further analyses.

Histology and immunohistochemical localizatiion of vascular endothelial growth factor (VEGF)
Prostate tissue were fixed for 1 day in paraformaldehyde solution (4% in phosphate-buffered saline (PBS) 0.1 M) at room temperature, dehydrated by graded ethanol and embedded in paraffin. Ten micrometres thick sections collected on glass slides, deparaffinized then stained with hematoxylin and eosin (H&E) for histopathological examination using light microscopy (Olympus BX51, Japan) associated to an Imaging system (Image Pro Plus 6.0).
Slices were deparaffinized and immersed in freshly prepared 3% H 2 O 2 , blocked with goat serum for 30 min, then treated with citrate buffer. The sections were rinsed with PBS and incubated at 4 °C overnight with VEGF antibody (Boster Biological Technology, Wuhan, China.), incubated with secondary antibody (goat anti-Rabbit IgG, Boster Biological Technology, Wuhan, China.) at 37 °C for 30 min. After washed with PBS, the sections were incubated in strept avidin-biotin complex at 37 °C for 30 min, and immersed in diaminobenzidine for 5 min. The haematoxylin-stained sections were dehydrated with ethanol and visualized with an optical microscope (Olympus BX51, Japan). The VEGF content was expressed as average optical density (IOD/Area).

Evaluation of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) in prostate tissue
Prostate samples were homogenized and assayed for MDA, SOD, GSH-Px and CAT using commercially available kits (MultiSciences Biotech Co., Ltd., Hangzhou, China). All the procedures were performed according to manufacturer's instructions of the kits.

Statistical analysis
All data were expressed as mean ± standard deviation. The results were analyzed by one-way ANOVA followed by LSD for multiple comparisons using SPSS 21.0 software for Windows (SPSS Inc., Chicago, IL). A P value of < 0.05 was considered significant.

Chemical ingredients of Fr. B
The BPI chromatograms of Fr. B by UPLC-QTOF-MS with both positive and negative ions were shown in Fig. 1. Ten flavonoid glycosides were assigned from Fr.  Table 1. Further, quantification of the 10 flavanoids glycosides in Fr. B was performed by HPLC with quercetin as internal standard, and compound 2 as index.
The results showed that 10 flavonoid glycosides were accounted for 54.96% of all substance of Fr. B, in which compound 1 was with a relative content of 11.1%, and compound 2 was with a relative content of 13% in Fr. B.

Effect of Fr. B on prostate morphology of BPH rats
There was no significant difference in rat weight among the groups along with the experiment. Prostate tissue collected from the sham rats showed normal architecture and histology, regular acini with cuboidal and low cylindrical epithelium with round nuclei showing basal alignment. While a significant disorganization of prostate tissue, irregular acinar shape with papillary projection into the lumen and foci of piling-up hyperplastic nodules were observed in the prostate tissue of rats after BPH induction. Finasteride, Pule'an, QCJ and Fr. B treatment could significantly improved the histological pattern and marked hyperplasia of prostate tissuein BPH rats (Fig. 2a). The expression of VEGF in the rat prostates was analyzed by immunohistochemical analysis. As shown in Fig. 2b, compared with the sham operation group, VEGF level in the prostate tissue of BPH group rats was significantly increased (P < 0.01

Effects of Fr. B on sex hormone levels in BPH rats serum
The basal levels of DHT, T and E 2 in serum of sham animals were showed in Fig. 3, those in serum collected from BPH animals showed marked increases (P < 0.01). Treatment with finasteride, Pule'an, QCJ and Fr. B considerably reduced DHT and DHT/E 2 levels (P < 0.01). However, significant increases were observed in T levels with QCJ and Fr. B administration (P < 0.05, Fig. 4). DHT is converted by the steroid enzyme 5α-reductase from T [21]. The production and accumulation of DHT in the prostate promote cell growth and induce hyperplasia [22]. The level of DHT in serum of rats was significantly lower than that of BPH rats, while the level of T was significantly higher, suggesting that Fr. B may play an anti-prostate hyperplasia role by inhibiting the production of DHT.

Effects of Fr. B on inflammatory factors in BPH rats serum
As shown in Fig. 4, serum levels of TNF-α and IL-6 were markedly elevated in BPH rats (P < 0.05). Oral administration of finasteride, Pule'an, QCJ and Fr. B to BPH rats considerably reduced TNF-α levels (P < 0.01).

Effects of Fr. B on MDA, SOD, GSH-Px and CAT levels in BPH rats prostates tissues
As shown in Fig. 5, homogenates of the prostates tissues from sham animals had a basal levels of MDA, while that from BPH rats showed a marked increase (P < 0.01). Oral administration of finasteride, Pule'an, QCJ and Fr. B to BPH rats significantly decreased levels of MDA (P < 0.01). Moreover, we also observed that the contents of SOD, GSH-Px and CAT in BPH rats prostates were significantly reduced, these are three important endogenous antioxidants in the body. Administration of finasteride, Pule'an, QCJ and Fr. B to BPH rats could significantly increase SOD levels of BPH rats (P < 0.05). Similarly, treatment with finasteride, high dose of QCJ and Fr. B also demonstrated significant trends of protection increasing the reduced levels of CAT and GSH-Px (P < 0.05) as well, whereas Pule'an group showed an increasing trend without statistically significance.

Discussion
Phytotherapy has been playing an important role in the treatment of BPH for over decades because of its mildness, effectiveness and low adverse effects. Lots of the researchers revealed that several kinds of constituents including the fatty acids, polyphenols, flavonoids, phytosterols, alkanoids may be responsible for BPH inhibitory activities of phytotherapy and the suggested mechanisms includes 5α-reductase inhibitor, α1-adrenoceptor antagonist, aromatase inhibitor, anti-androgen, growth factor inhibitor, and so on [23][24][25]. The special chemical structure of flavonoids makes them have good anti-BPH properties [26]. Total flavanol glycosides from Abacopteris penangiana and its acid hydrolysate [27], total flavonoid extract of Pteris multifida [15] and dihydroquercetin [28], were reported to exert BPH protective effect through regulating inflammatory responses and reducing oxidative stress. In this study, we found that the active fraction Fr. B of P. utilis leaves riched in flavanoids, of which 10 identified flavonoid glycosides accounted for 54.96% of all Fr. B substances, which contributed to BPH reduction by mechanisms related with anti-oxidant, antiinflammatory effect, reduction of DHT/E2 ratio, and inhibition of growth factor. Among these 10 identified flavonoid glycosides, 4 compounds are kaempferol-O-glycosides (peak 2, 4, 6, 9), 3 compounds are quercetin-O-glycosides (peak 1, 3,8), and 3 compounds are isorhamnetin-O-glycosides (peak 5, 7, 10). It was reported that kaempferol exhibited its androgeniclike activity and served as a selective androgen receptor modulator that contributed to androgen-related BPH development [29]. Kaempferol was revealed to be much better inhibitor of the type 2 than type 1 isozyme, quercetin was proved to be a potent inhibitor of the type 1 5α-reductase [30]. Moreover, kaempferol and its glycosides (kaempferol3-(3-E-p-coumaroylα-L-rhamnopyranoside), kaempferol 3-(2,3-di-E-pcoumaroyl-α-L-rhamnopyranoside)) from the pollen of Brassica napus L. were found to exhibit down-regulation of prostate specific antigen in LNCaP cells [31]. Yin et al [32] once reported the kaempferol-3-Oα-L-rhamnopyranosyl-(1 → 6)-β-D-glucopyranoside isolated from the Adina rubella leaves, the extract of which exhibited anti-oxidative and anti-inflammatory activities and 5α-reductase inhibition associated with BPH. Similarly, Epilobium angustifolium exhibited the therapeutic potential against BPH, and its active compounds included both kaempferol and quercetin as well as their glycosides [33]. The chemical investigation of the aerial parts of the fern Asplenium ceterach, one traditional medicine to treat BPH, revealed the presence of kaempferol and quercetin glycosides [34]. In addition, two quercetin glycosides (quercetin5-Oβ-D-glucopyranoside, quercetin 3-O-β-L-rhamnopyranoside) are the main active components against anti-BPH of aqueous extracts from Saxifraga stolonifera [35]. So, the flavonoid glycosides identified from Fr. B should be potential anti-BPH ingredients of P.
utilis, for further purification and pharmacological investigation. In vitro and in vivo studies describe oxidative stress as a major pathway involved in the occurrence of BPH [36,37]. High plasma peroxide levels were found in BPH patients compared with controls [38,39]. Circulating MDA levels were found to be significantly higher in BPH patients than in healthy donors [38]. However, other works found circulating MDA levels in BPH patients similar to those in controls [36]. In our study, the level of MDA in prostate of BPH rats was significantly increased, indicating the prostate tissue was in a state of oxidative damage. Fr. B could significantly decrease the level of MDA in prostate of BPH rats. Normally, highly oxidative stresses are removed by natural protective mechanism, the superoxide dismutase enzyme system, such as SOD, GSH-Px and CAT [17,40,41]. Fr. B could significantly increase the content of antioxidant enzymes (SOD, GSH-Px and CAT) and enhance the antioxidant capacity of rats. Prostate enlargement due to chronic inflammatory process may progressively conduce to BPH progression. Therefore, inflammation is a therapeutic target for BPH [42]. Although Fr. B had no significant decrease in serum IL-6 in BPH rats, it had a significant effect on TNF-α, suggesting its potential to improve BPH-related inflammation. These results suggested that Fr. B attenuate symptoms of BPH, at least in part, by decreasing the proinflammatory cytokines secretion and oxidative stress.
In addition, androgens are essential for the development and differentiated function of the prostate, as well as for proliferation and survival of prostatic cells [43,44]. It is clear that androgens, estrogens [45] and growth factors [46] contribute to the BPH, but the exact etiology remains unknown. In this study, increased DHT levels and decreased T levels, as well as increased DHT/ E 2 resulting from BPH induction, were significantly improved by Fr. B treatment. This reflected the androgens regulation potential mechanism of Fr. B on treating BPH. Recently, increasing evidences suggested that prostate growth was under the indirect control of androgens through the mediation of different growth factors [47]. VEGF is a major inducer of angiogenesis as it influences endothelial cell growth. The immunohistochemical assay showed that the expression of VEGF in the prostatic tissue with BPH rats were significantly increased compared normal prostatic tissue [48]. We also found that Fr. B could significantly decrease the expression of VEGF in prostate tissue of BPH rats. Its specific mechanism and signal pathway need to be further discussed.

Conclusion
Collectively, the results of present study showed that Fr. B prepared from the water extract of P. utilis leaves attenuated symptoms of BPH through multiple mechanisms including reduction of DHT/E2 ratio, inhibition of growth factor, anti-inflammation and anti-oxidation. Ten flavonoids were assigned from Fr. B by UPLC-QTOF-MS. These results support that Fr. B should be further explored as a prospective natural foods or supplements for BPH treatment.