Cancer, also called malignancy is an abnormal growth of cells. An estimated 9.6 million deaths were caused by cancer in 2018 . It is the second leading cause of death globally. Breast cancer, the most common cancer among women and prevalent in underdeveloped countries, is one of the leading causes of morbidity and mortality for women worldwide . Hepatocellular carcinoma (HCC), the most common primary malignancy of the liver, is a leading cause of death in people with cirrhosis . Significant progress has been made in the diagnosis and treatment of HCC using multidisciplinary approaches of surgical and non-surgical , including systematic chemotherapy . Colorectal cancer is caused by several risk factors including genetic and environmental factors, lifestyle, and gut microbiota. Because of the undesirable side effects and efficacy, a variety of cytotoxic drugs are incompetent. There is a need for novel anticancer compounds of having no undesirable side effects. In eukaryotes apoptosis plays an essential role in regulating tissue development and maintaining homeostasis [6–8], deregulation of which is one of the hallmarks of cancer .
One of the reasons of resistance of many common pathogens to commonly used therapeutic agents, such as antibiotics  is the formation of biofilms. Biofilms are surface-attached microbial communities in which microbial cells are entrenched in extracellular polymeric substances (EPS) formed by the cells themselves. As a result, biofilms serve as effective physical barriers to antibiotic and nutrient penetration . For example, S. aureus, a Gram-positive bacterium and causative agent of nosocomial infection causes significant morbidity and mortality in hospitalized patients because of its ability to adhere to the surfaces of indwelling medical devices.
There are about 200 species of mycobacteria including M. tuberculosis and other non-tuberculosis mycobacteria (NTM) species that cause several types of diseases in humans. Tuberculosis, caused by M. tuberculosis is a leading cause of 1.5 million deaths each year and a major contributor to antimicrobial resistance. Non-tuberculosis Mycobacteria (NTM), once thought to be harmless environmental saprophytes and dangerous to immunocompromised and lung-defective individuals, are now causing a spectrum of diseases that include tuberculosis (TB)-like pulmonary and extrapulmonary disease, visceral and disseminated disease, and cervical lymphadenitis to immunocompetent individuals . In Saudi Arabia and other gulf countries, M. fortuitum and M. abscessus were found to be approximately 36% and 21% of the clinical isolates of mycobacterium .
Myrtus communis or Myrtle (Arabic name: Aas or Hadas), belonging to the Myrtaceae (Saudi Arabia refers it as Mesk Ul-madena), is a notable therapeutic herb. It is an evergreen aromatic and medicinal plant inhabitant of the Mediterranean region, along with other nations such as Iraq, Jordan, the Southern and Eastern provinces of Saudi Arabia , and Iran in the Middle East. The various parts of this herb such as its berries, leaves, and fruits have been used extensively as a folk medicine for several centuries. The herb is used traditionally for the treatment of disorders such as inflammation, diarrhea, hemorrhoid, peptic ulcer, pulmonary, and skin diseases. It possesses a broader spectrum of pharmacological and therapeutic effects such as anti-diabetic, antioxidative, antiviral, antibacterial, antifungal, anticancer, hepatoprotective, and neuroprotective activity . Not much progress has been made on understanding the anticancer activity of M. communis, except few studies, wherein mostly essential oils and methanol extract of several medicinal plants have been screened for anticancer activity .
In the present study, the ethanolic leaf extract of M. communis was investigated for its effect on cell viability, cell cycle arrest, and apoptosis of four different cancer cell lines, viz, human hepatocellular carcinoma cell line (HepG2), colorectal adenocarcinoma cell line (HCT116), breast adenocarcinoma cell line (MCF-7), and human cervix adenocarcinoma cell line (HeLa). Furthermore, the mechanism underlying apoptosis was also investigated. This is the first report of the anticancer activity of the M. communis leaf extract against the above-mentioned cancer cell lines and the underlying mechanism of apoptosis.
Antibacterial activity of the ethanolic leaf extract of Myrtus communis was also investigated against diverse mycobacterial strains including laboratory and reference strains, viz, M. abscessus, M. avium, M. fortuitum, M. kansasii, M, M. mucogenicum, M. tuberculosis, M. tuberculosis Rif-R, and M. xenopi. Furthermore, we investigated the effect of M. communis extract on biofilm formation in S. aureus and M. smegmatis, the latter being a model organism to study M. tuberculosis. Collectively, these results indicate that M. communis leaf extract is a promising herbal extract, which could be developed further as anticancer and antimycobacterial agents to treat diverse types of cancers, tuberculosis, and other mycobacterial diseases, including S. aureus infections. However, further evaluation, active compound isolation, in-vitro and in-vivo investigations of M. communis leaf extract constituents are recommended.