•  doi: 10.1155/2017/9217567
• Published online 2017 Mar 16

Negar Jamshidi and Marc M. Cohen ^* 

Abstract

Tulsi, also known as holy basil, is indigenous to the Indian continent and highly revered for its medicinal uses within the Ayurvedic and Siddha medical systems. Many in vitro, animal and human studies attest to tulsi having multiple therapeutic actions including adaptogenic, antimicrobial, anti-inflammatory, cardioprotective, and immunomodulatory effects, yet to date there are no systematic reviews of human research on tulsi’s clinical efficacy and safety. We conducted a comprehensive literature review of human studies that reported on a clinical outcome after ingestion of tulsi. We searched for studies published in books, theses, conference proceedings, and electronic databases including Cochrane Library, Google Scholar, Embase, Medline, PubMed, Science Direct, and Indian Medical databases. A total of 24 studies were identified that reported therapeutic effects on metabolic disorders, cardiovascular disease, immunity, and neurocognition. All studies reported favourable clinical outcomes with no studies reporting any significant adverse events. The reviewed studies reinforce traditional uses and suggest tulsi is an effective treatment for lifestyle-related chronic diseases including diabetes, metabolic syndrome, and psychological stress. Further studies are required to explore mechanisms of action, clarify the dosage and dose form, and determine the populations most likely to benefit from tulsi’s therapeutic effects.

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1. Introduction

Tulsi in Hindi or Tulasi in Sanskrit (holy basil in English) is a highly revered culinary and medicinal aromatic herb from the family Lamiaceae that is indigenous to the Indian subcontinent and been used within Ayurvedic medicine more than 3000 years. In the Ayurveda system tulsi is often referred to as an “Elixir of Life” for its healing powers and has been known to treat many different common health conditions. In the Indian Materia Medica tulsi leaf extracts are described for treatment of bronchitis, rheumatism, and pyrexia [1]. Other reported therapeutic uses include treatment of epilepsy, asthma or dyspnea, hiccups, cough, skin and haematological diseases, parasitic infections, neuralgia, headache, wounds, and inflammation [2] and oral conditions [3]. The juice of the leaves has been applied as a drop for earache [4], while the tea infusion has been used for treatment of gastric and hepatic disorders [5]. The roots and stems were also traditionally used to treat mosquito and snake bites and for malaria [5].

Three types of tulsi are commonly described. Ocimum tenuiflorum (or Ocimum sanctum L.) includes 2 botanically and phytochemically distinct cultivars that include Rama or Sri tulsi (green leaves) and Krishna or Shyama tulsi (purplish leaves) [6, 7], while Ocimum gratissimum is a third type of tulsi known as Vana or wild/forest tulsi (dark green leaves) [8, 9]. The different tulsi types exhibit vast diversity in morphology and phytochemical composition including secondary metabolites, yet they can be distinguished from other Ocimum species by the colour of their yellow pollen, high levels of eugenol [10], and smaller chromosome number [11]. Despite being distinct species with Ocimum tenuiflorum having six times less DNA than Ocimum gratissimum [11], they are traditionally used in the same way to treat similar ailments [5]. For consistency, this review uses the term tulsi to refer to both Ocimum tenuiflorum or Ocimum gratissimum.

Tulsi has been the subject of numerous scientific studies and its pharmacological and wide range of therapeutic applications are the subject of more than one hundred publications during the last decade alone. Numerous in vitro and animal studies attest to tulsi leaf having potent pharmacological actions that include adaptogenic [12–14], metabolic [15–17], immunomodulatory [18–20], anticancer [21–23], anti-inflammatory [24, 25], antioxidant [26, 27], hepatoprotective [28, 29], radioprotective [30, 31], antimicrobial [32–35], and antidiabetic effects [36–38] that have been extensively reviewed previously [39–45].

Preclinical studies have demonstrated that tulsi increases swimming survival times in mice and prevents stress-induced ulcers in rats [46] with antistress effects comparable to antidepressant drugs [47]. Similarly, recent studies report leaf extracts from ethanolic and aqueous tulsi protects rats from stress-induced cardiovascular changes [48, 49]. Studies in animal models have further shown that the leaf extract of tulsi possesses anticonvulsant and anxiolytic activities [50, 51]. Several animal studies conducted over the past fifty years report that ingestion of tulsi leaves improves both glucose and lipid profiles in normal and diabetic-induced animal models [36, 38, 52–58]. Tulsi aqueous leaf extract intramammary infusion has also showed promising effect on improving the immune response in bovine models [59].

In addition to the extensive literature documenting in vitro and animal research, studies on the use of tulsi as part of a polyherbal formulation in humans has been systematically reviewed [60]. To date, however, there are no systematic reviews on the clinical efficacy and safety of tulsi as a single herbal intervention in humans. The objective of this review was therefore to summarize and critically appraise human clinical trials of tulsi in order to assess the current evidence on tulsi’s clinical efficacy and safety.

Reference:

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5376420/