Chemical composition and in vitro antioxidant evaluation of a water-soluble Moldavian balm (Dracocephalum moldavica L.) extract

Abstract

The chemical composition and antioxidant properties of a water-soluble extract of Moldavian balm (Dracocephalum moldavica L., syn. Moldavian dragonhead) prepared by hydrodistillation are presented in this study. The total phenol content was estimated as gallic acid equivalents by the Folin-Ciocalteu reagent method, while the qualitative–quantitative composition of the extract was determined by high performance liquid chromatography coupled with photodiode array detection. The antioxidant properties assessed included iron(III) reduction and iron(II) chelation and 1,1-diphenyl-2-picrylhydrazyl, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) and superoxide anion free radical scavenging. In addition, the ability of the extract to protect 2-deoxy-d-ribose and bovine brain-derived phospholipids against hydroxyl radical-mediated degradation was assessed. The extract principally contained polar compounds including hydroxycinnamic acids and flavonoids, with caffeic and ferulic acids, luteolin-7-O-glucoside, rosmarinic acid, luteolin and apigenin being identified from their chromatographic behavior and spectral characteristics. The Moldavian balm extract demonstrated activity in all the antioxidant assays; however, it was not as potent as the positive control except in the phospholipid-based assay where its hydroxyl radical scavenging activity was statistically indistinguishable from that demonstrated by Pycnogenol.

Introduction

Reactive oxygen species (ROS), e.g. superoxide anion and hydroxyl radicals, hydrogen peroxide and singlet oxygen, are formed as a result of normal metabolic activity (Halliwell & Gutteridge, 1989a) or as byproducts of oxidative reactions involving xenobiotics (Stohs, 1995). In vivo, such species are securely coupled at their site of generation or are detoxified by endogenous antioxidative defences so as to preserve optimal cellular function. In pathological conditions, however, the detoxifying mechanisms are often inadequate as excessive quantities of ROS can be generated. This resulting pro-oxidant shift, a process known as oxidative stress, can result in the degradation of cellular components, viz., DNA, carbohydrates, polyunsaturated lipids and proteins, or precipitate enzyme inactivation, irreversible cellular dysfunction and ultimately cell death if the pro-oxidant-antioxidant balance is not restored. Furthermore, not only do ROS play a cardinal role in the aetiology of numerous diseases (Halliwell & Gutteridge, 1989b), they also contribute to the deterioration of foodstuffs (Sasaki, Ohta, & Decker, 1996), cosmetics and pharmaceutical preparations (Branen & Davidson, 1997).

Recently, interest in the discovery of natural antioxidants has risen exponentially, principally for three reasons: (1) the overwhelming epidemiological and clinical evidence suggesting an inverse relationship between the consumption of vegetables and fruits and the risk of developing chronic disease, e.g. cancer; (2) concerns regarding the safety of the chronic consumption of synthetic compounds traditionally used as preservatives in foods and beverages; and (3) the public's belief that phytochemicals are inherently safer than synthetic chemicals. Principal candidates in this discovery process have been herbs, spices, and medicinal plants.

Moldavian balm (Dracocephalum moldavica L., syn. Moldavian dragonhead) is a perennial herb belonging to the family Lamiaceae (Labiatae). This plant is native to central Asia and is naturalised in eastern and central Europe. In Iran, it is predominantly found in the north of the country, especially in the Albourz Mountains, where it is known as ‘Badarshoo’. It is frequently consumed as a food additive (e.g. in yogurt) or as an infusion for its organoleptic properties. As a herbal drug, it is used in stomach and liver disorders, headache and congestion (Rechinger, 1986).

Very few articles deal with the nonvolatile chemistry (Aynehchi, Sormaghi, Amin, Soltani, & Qumehr, 1982; Kakasy, Lemberkovics, Kursinszki, Janicsak, & Szoke, 2002) or antioxidant properties of Moldavian balm (Povilaityte & Venskutonis, 2000; Povilaityte, Cuvelier, & Berset, 2001). Thus, as part of our ongoing investigation into the phytochemistry and antioxidant properties of aromatic and medicinal flowering taxa, we have investigated the phytochemistry [total phenol content and qualitative-quantitative composition] and antioxidant [iron reductive and chelating and 1,1-diphenyl-2-picrylhydrazyl, 2,2′-azinobis(3-ethylbenzothiazoline-6-sulphonic acid), superoxide anion and hydroxyl radical scavenging] properties of a hydrodistilled water-soluble Moldavian balm extract.