Two new neo-clerodane diterpenoids from Scutellaria barbata

Chemical Constituents, Anti-Tumor Mechanisms, and Clinical Application: A Comprehensive Review on Scutellaria barbata

With the increasing global incidence and mortality rates of cancer, the development of novel anti-tumor drugs has become particularly urgent. Scutellaria barbata D. Don, a perennial herb belonging to the genus Scutellaria in the family Lamiaceae, has aroused extensive attention for its medicinal value in recent years. This article presents an exhaustive review of the flavonoid, diterpene, and other chemical constituents harbored within Scutellaria barbata, delving into the intricate mechanisms by which these compounds orchestrate their anti-tumor effects via diverse biological pathways. Remarkably, these compounds distinguish themselves through their capability to regulate cellular signaling, inhibit cancer cell proliferation, trigger apoptosis, disrupt angiogenesis, and bolster immune responses. These anti-tumor effects are achieved through strategic modulation of pivotal signaling cascades, particularly the PI3K/Akt/mTOR, MAPK, and NFκB pathways. In addition, this article also summarizes the clinical applications of Scutellaria barbata in tumor treatment, especially its potential in alleviating the side effects of radiotherapy and chemotherapy and improving patients' quality of life. In conclusion, this review comprehensively summarizes and analyzes the chemical constituents, anti-tumor mechanisms, and clinical applications of Scutellaria barbata, with the aim of systematically reviewing the existing research results and exploring potential future research directions.

Diterpenes of Scutellaria spp.: Phytochemistry and pharmacology

Scutellaria genus, a member of the Lamiaceae family, distributed worldwide and known as skullcaps, contains a wide range of pharmacologically active constituents including flavonoids and diterpenes. There are different classes of diterpenes in the plant kingdom, of which many have medicinal applications. Scutellaria spp. contain neo-clerodane diterpenes, a large group of naturally occurring specialized metabolites found in both plant species and in organisms from other taxonomic groups, such as fungi, bacteria, and marine sponges. Although many phytochemical studies have been established reporting interesting specialized diterpene structures from Scutellaria spp., there has not been a comprehensive study reviewing these compounds. Hence, the present review reports on natural diterpenoids from the Scutellaria genus and their pharmacological activities. For this purpose, the scientific databases including Scopus, PubMed, and Google Scholar were searched using the keywords "Scutellaria" and "Diterpenes" or "Diterpenoids". The literature review showed that up to now, more than 300 diterpenes have been isolated and reported from the Scutellaria genus, belonging to neo-clerodane scaffolds. Anticancer, antifeedant, phytotoxic, antimicrobial, and nitric oxide production inhibitory activities are the most reported properties for the diterpenoids from the Scutellaria genus. Diterpenes of Scutellaria spp. have therapeutic potentials to be used for the treatment of different diseases. Further phytochemical, pharmacological, and clinical studies are required in this regard.

neo-Clerodane Diterpenoids from the Aerial Parts of Scutellaria barbata with Anti-Inflammatory Activity

The bioactivity-guided isolation on the Scutellaria barbata extract resulted in the purification of four undescribed neo-clerodane diterpenoids, scuttenlines A-D (1-4), alone with 20 known diterpenoids (5-24). The chemical structures of them were elaborated by extensive spectroscopic means, including 1D, 2D-NMR and HR-MS. The anti-inflammatory potential ability of 1-24 was screened in lipopolysaccharide-stimulated mouse RAW 264.7 cells. Scuttenline C (IC₅₀ =1.9 μM) and 18 (IC₅₀ =3.7 μM) exhibited potent activity to inhibit NO production.

Effect of Chinese Herbal Medicine Therapy on Overall and Cancer Related Mortality in Patients With Advanced Nasopharyngeal Carcinoma in Taiwan

Nasopharyngeal carcinoma (NPC) is a head and neck cancer involving epithelial squamous-cell carcinoma of the nasopharynx that mainly occurs in individuals from East and Southeast Asia. We investigated whether Chinese herbal medicine (CHM) as a complementary therapy offers benefits to these patients. We retrospectively evaluated the Taiwan Cancer Registry (Long Form) database for patients with advanced NPC, using or not using CHM, between 2007–2013. Cox proportional-hazard model and Kaplan‒Meier survival analyses were applied for patient survival. CHM-users showed a lower overall and cancer-related mortality risk than non-users. For advanced NPC patients, the overall mortality risk was 0.799-fold for CHM-users, after controlling for age, gender, and Charlson comorbidity index (CCI) score (Cancer stages 3 + 4: adjusted hazard ratio [aHR]: 0.799, 95% confidence interval [CI]: 0.676–0.943, p = 0.008). CHM-users also showed a lower cancer-related mortality risk than non-users (aHR: 0.71, 95% CI: 0.53–0.96, p = 0.0273). Association rule analysis showed that CHM pairs were Ban-Zhi-Lian (BZL; Scutellaria barbata D.Don) and For single herbs, Bai-Hua-She-She-Cao (Herba Hedyotis Diffusae; Scleromitrion diffusum (Willd.) R.J.Wang (syn. Hedyotis diffusa Willd.) and Mai-Men-Dong (MMD; Ophiopogon japonicus (Thunb.) Ker Gawl.), and Gan-Lu-Yin (GLY) and BHSSC. Network analysis revealed that BHSSC was the core CHM, and BZL, GLY, and Xin-Yi-Qing-Fei-Tang (XYQFT) were important CHMs in cluster 1. In cluster 2, ShengDH, MMD, Xuan-Shen (XS; Scrophularia ningpoensis Hensl.), and Gua-Lou-Gen (GLG; Trichosanthes kirilowii Maxim.) were important CHMs. Thus, as a complementary therapy, CHM, and particularly the 8 CHMs identified, are important for the treatment of advanced NPC patients.

A review of the ethnopharmacology, phytochemistry, pharmacology, and quality control of Scutellaria barbata D. Don

ETHNOPHARMACOLOGICAL RELEVANCE

Scutellaria barbata D. Don (S. barbata) is a well-known perennial herb that is used in traditional Chinese and Korean medicine. In China, it is known as Ban Zhi Lian, while in Korea, it is known as Banjiryun. In the Traditional Chinese Medicine (TCM) system, S. barbata has heat-clearing and detoxifying properties (Qingre Jiedu in Chinese).

AIM OF THE REVIEW

To provide a systematic review on current multifaceted understanding of S. barbata, with particular emphasis on the correlation between its traditional applications and pharmacological activities.

MATERIALS AND METHODS

All available S. barbata-related information from internet databases, including PubMed, Science Direct, Elsevier, China National Knowledge Internet, and Google Scholar (up to October 2018) were searched. Additional information was gathered from classical books on Chinese Herbals, Chinese Pharmacopoeia, and so on.

RESULTS

In the TCM system, S. barbata is mainly prescribed for its heat-clearing and detoxifying effects. More than 203 compounds have been isolated and identified from this herb, with neo-clerodane diterpenoids and flavonoids as the main compounds. Most neo-clerodanes have been demonstrated to have cytotoxic effects against different cancer cell types in vitro. The S. barbata extracts exhibited anti-inflammatory, anti-microbial, antitumor, and other pharmacological activities. To add, flavonoids, including wogonin, baicalein, apigenin, naringenin, and scutellarin, were identified as the key to quality control.

CONCLUSIONS

The heat-clearing effects of S. barbata could be attributed to its anti-inflammatory and hepatoprotective activities, whereas its detoxifying effects might be due to the anti-microbial functions of neo-clerodane diterpenoids and flavones. S. barbata may display anti-tumor effects and through active ingredient analysis, neo-clerodane diterpenoids are suggested to be its representative compounds. Overall, many pre-clinical studies have been conducted but very little concrete evidences are available on its specific effects, which are of therapeutic relevance.

From Scutellaria barbata to BZL101 in Cancer Patients: Phytochemistry, Pharmacology, and Clinical Evidence

Scutellaria barbata D.Don is a popular Chinese medicinal plant documented to treat cancer patients in traditional Chinese medicine (TCM). A botanical new investigational drug for breast cancer BZL101 (FDA IDN# 59521) was previously developed in the United States from the aqueous extract of the aerial parts from S. barbata. The early phase 1A and 1B clinical trials show its favorable toxicity profiles, good clinical tolerance, and promising efficacy for patients with metastatic breast cancer. To further evidence the phytopharmacology research, drug development, and anticancer use of this herb, a systematic literature review was performed herein on the phytochemistry, pharmacology, and specifically anticancer clinical evidence. A systematic review of the literature on phytochemical and pharmacological properties of the plant related to cancer treatment employed several web-based scientific databases including Wanfang (Chinese), Pubmed, Web of Science, and Elsevier. Key words included Scutellaria barbata, Ban Zhi Lian, cancer, and tumor. Based on critical quality criteria, only 8 out of 69 reports related to clinical studies of cancer patients in China. This review covered the available literature up to July 2019. The anticancer effects of S. barbata can be explained by the presence of various flavonoids and diterpenoids alkaloids. The underlying mechanisms are primarily summarized as cyclin/cyclin-dependent kinase (CDK)-modulated cell cycle arrest and mitochondria-mediated apoptotic death. The highly cancer-cell selective cytotoxicity and detoxifying effects of S. barbata contribute to a favorable clinical profile and enhanced quality of life for the cancer patient, thereby demanding further study as an adjuvant or alternative to conventional chemotherapy. The phytochemical and pharmacological studies reviewed strongly underpin a fundamental understanding of the anticancer activity of S. barbata and support ongoing clinical trials. The further safety verification and clinical trials are expected to progress S. barbata-based development to finally transform the traditional TCM herb S. barbata to the valuable anticancer drug.

Scutellaria: Debates on the anticancer property

The widespread use of plants as accessible anticancer agents leads to the identification of many natural source chemotherapeutic agents. Scutellaria one of the popular genus of flowering plants has been used for various human illnesses for thousands of years. Scutellaria has anti-metastatic, anti-proliferative, anti-invasion, anti-angiogenic and apoptosis effects in vitro as well as in vivo. Despite numerous reports on the cytotoxic-antitumor activity of the plant, there are still some issues need further consideration. Issues such as unjustified interpretations, lack of attention to the pharmacokinetics profile and weak study design may affect the final decision about the use of plants as anticancer agents and possibly needs reconsideration. In this review, we have summarized the potential health benefits of Scutellaria and its active components also the underlying mechanism of cytotoxicity and antitumor activity. Meanwhile we have discussed concerns may interfere with the precise conclusion.

Clerodane diterpenes: sources, structures, and biological activities

Covering: 1990 to 2015The clerodane diterpenoids are a widespread class of secondary metabolites and have been found in several hundreds of plant species from various families and in organisms from other taxonomic groups. These substances have attracted interest in recent years due to their notable biological activities, particularly insect antifeedant properties. In addition, the major active clerodanes of Salvia divinorum can be used as novel opioid receptor probes, allowing greater insight into opioid receptor-mediated phenomena, as well as opening additional areas for chemical investigation. This article provides extensive coverage of naturally occurring clerodane diterpenes discovered from 1990 until 2015, and follows up on the 1992 review by Merritt and Ley in this same journal. The distribution, chemotaxonomic significance, chemical structures, and biological activities of clerodane diterpenes are summarized. In the cases where sufficient information is available, structure activity relationship (SAR) correlations and mode of action of active clerodanes have been presented.

Neo-clerodane diterpenoids from Scutellaria barbata with activity against Epstein-Barr virus lytic replication

Bioassay-guided fractionation was conducted on an EtOAc-soluble extract of the whole plants of Scutellaria barbata, monitored by inhibition of Epstein-Barr virus (EBV) lytic replication. Twenty-six neo-clerodane diterpenoids were isolated, of which 13 are new (1-13, scutolides A-L) and 13 previously known (14-26). The structures of 1-13 were elucidated by analysis of their NMR and MS spectroscopic data. Furthermore, the configurations of the new compounds 1 and 11 were confirmed by single-crystal X-ray diffraction. All of the isolated compounds were evaluated for inhibitory effects against EBV lytic replication. Eleven compounds (3, 4, 6, 11, 12, 15, 16, 17, 20, 22, and 24) exhibited moderate to potent inhibition, with EC50 values from 3.2 to 23.6 μM and selective index (SI) values from 2.1 to 109.2. More specifically, the new compound 4 showed the most potent activity, with EC50 and SI values of 3.2 μM and 46.1, respectively, while compound 24 (EC50 = 16.4 μM) exhibited the highest SI of 109.2. This study is the first to report that neo-clerodane diterpenoids demonstrate significant inhibition against EBV lytic replication.

Two new phenols from Scutellaria barbata

Two new phenols, 2(S)-2’,7-dihydroxy-5,8-dimethoxyflavanone (1) and (S)-2-(4-hydroxyphenyl)-6-methyl-2,3-dihydro-4H-pyran-4-one (2), were isolated from the ethanol extract of Scutellaria barbata. Their structures were elucidated on the basis of spectroscopic analysis.

Scutebarbatines W-Z, new neo-clerodane diterpenoids from Scutellaria barbata and structure revision of a series of 13-spiro neo-clerodanes

Four new neo-clerodane diterpenoids, scutebarbatines W-Z (1-4), were isolated from the ethanol extract of Scutellaria barbata (Labiatae), and their structures were elucidated on the basis of extensive spectroscopic studies. In addition, the proposed structures of at least seven 13-spiro subtype neo-clerodanes: scutehenanine B (5), scutebarbatine G (6), 6-O-nicotinoylscutebarbatine G (7), barbatin A (8), 6,7-di-O-nicotinoylscutebarbatine G (9), 6-O-nicotinoyl-7-O-acetylscutebarbatine G (10), and scutebarbatine F (11), reported by Dai and co-workers from the same species, were incorrectly assigned and have been revised by reanalysis of the published NMR data.

LC-MS-SPE-NMR for the isolation and characterization of neo-clerodane diterpenoids from Teucrium luteum subsp. flavovirens (perpendicular)

neo-Clerodane diterpenes of plant origin are molecules difficult to monitor due to their nonspecific UV/vis absorption. The present work describes for the first time the application of the LC-MS-SPE-NMR technique for the isolation and characterization of three new neo-clerodane diterpenes, 3beta-hydroxyteucroxylepin and teuluteumin A and teuluteumin B, from Teucrium luteum subsp. flavovirens, harvested from two different locations.