## 1 Introduction  
Plant-derived bioactive compounds have always served a sustainable resource for drug, nutraceuticalul and cosmeceutical development. However, the first step in this endeavor, is the selection of the best plant part and an appropriate extraction protocol which yields best activity. In this respect, several conventional and non-conventional extraction methods have been designed and used in a plethora of studies. Among these methods, soxhlet, maceration or percolorization are considered as conventional methods. However, the conventional methods have some disadvantages such as the use of high volume of solvent and long extraction times. In this sense, recently some new and improved techniques have emerged as green or non-conventional extraction techniques. Ultrasound-assisted, homogenizer-assisted, and microwave-assisted extractions are classified as the green extraction methods. The green extraction methods allows working with low volume of solvents as well as shorter extraction times. In addition, these methods gave higher extraction yields. Altogether, the selection of the best extraction method is one of the most popular subjects in the chemical and biological investigations [1; 2]. In the present study, _Calendula officinalis_ (Asteraceae), an important species of the genus _Calendula_ and is well known for its medicinal properties [3], was investigated for biological activity based on different extraction protocols. Also known as pot marigold, _C. officinalis_ has been cultivated as a food and medicinal plant since the Middle Ages and the colorant made from this plant was used in the ancient Greece and Rome and by early Indian and Arabic population [4]. In previous studies, the flowers and leaves of _C. officinalis_ have been reported as a source of biologically active compounds. For example, in a study conducted by [PERSON] et al [5] described that the presence of hydroxycinnamic acids and flavonoids in the flowers and leaves of _C. officinalis_. Similarly, quercetin and apigenin derivatives were found to be in the hydroalcoholic extract of flower [6]. In addition to phenolics, the leaves and flowers contained saponins, triterpen, essential oils, and carotenoids [7; 8; 9; 10; 11]. _C. officinalis_ seeds are particularly rich in calendic acid which is used in cosmetic formulations. The flowers are exploited as a commercial source of lutein. The cell rejuvenates, healing, anti-inflammatory, soothing and skin softening properties of _C. officinalis_ flower support its use in skin care products [3]. The antimicrobial and antifungal properties of _C. officinalis_ flower extract support its application for the treatment of inflammation and skin wounds [12]. The application of _C. officinalis_ cream balm to diabetic patients' feet prevented infection, reduced itching, redness, dryness, pain, and promoted the disappearance of scars [13]. Favorable proliferation and adhesion to fibroblast cell as well as antibacterial properties was observed while incorporating _C. officinalis_ extract to an electrospun fiber scaffold consisting of poly (\(\varepsilon\)-caprolactone), zein, and gum Arabic as compared to plain PCL/zein/GA scaffold, thereby suggesting the possible application of _C. officinalis_ embedded scaffolds biomaterial for skin regeneration [14]. The Food and Drug Administration (FDA) has classified _C. officinalis_ as a GRAS (Generally Recognized as Safe) substance [15]. Edible _Calendula_ flowers possessing nutritional properties and being rich in quinic acid and \(\alpha\)-tocopherol, were used for the preparation of omelets, salads, and as accompaniment with cheese in Medieval France [16]. The flower extract was used to manage measles, smallpox; the flower juice was used to treat skin diseases, ulcers, costiveness, jaundice, fever, wounds, and to suppress menstruation, promote sweating, and prevent suppuration; infusion of the plant was used to manage anemia and the ointment was used against bruises, sores, cracks, and cuts in the hands [7]. _C.