ABSTRACT
CONTEXT: Hypertension (HTN) is a chronic medical condition affecting nearly 1 billion people worldwide. Yoga, typically thought of as a series of physical postures, also includes breath practices and meditation. It has the potential to reduce of blood pressure (BP) through a combination of stress reduction and modification of the physiology of the autonomic nervous system. Pranayama is the art of prolongation and control of breath and helps bring conscious awareness to breathing patterns. OBJECTIVES: The study aimed to measure the effects of Sheetali and Sheetkari pranayamas on BP, the autonomic nervous system, and respiratory functions among hypertensive participants. DESIGN: The study design was a randomized controlled trial. SETTING: The study was carried out at a clinical research center at Sri Dharmasthala Manjunatheshwara Yoga and Nature Cure Hospital (Belthangady, India). PARTICIPANTS: The participants were 60 hypertensive individuals, aged from 25 to 65 y, who were recruited from the general population located in and around Ujire, Belthangady, Karnataka, India. INTERVENTION: Participants were randomly assigned either to an intervention group (n = 30) or wait-list control groups (n = 30). The intervention included 2 types of pranayama breath practices (ie, Sheetali and Sheetkari) each practiced for 10 min/d. OUTCOME MEASURES: BP and autonomic and respiratory functions were measured at baseline and postintervention. RESULTS: Compared to control, the intervention group showed a significant mean decrease in (1) systolic blood pressure (SBP)-16.2 mm Hg (P ≤.001), (2) respiratory rate-3.4 rpm (P<.001), and (3) heart rate-6.7 bpm (P ≤.01). Heart rate variability parameters were improved in the intervention group, including high-frequency power (P = .01), the number of pairs of successive NN intervals that differ by more than 50 ms (ie, NN50, P = .01), and the proportion of NN50 divided by total number of NNs (ie, pNN50, P = .05). CONCLUSIONS: Sheetali and Sheetkari pranayamas appear effective for lowering SBP in individuals with HTN. Within-group results suggest that the changes may be mediated through a modification in tone of the sympathovagal nervous system.
ABSTRACT
Ever since the discovery of the porphyrin ring in "pigments of life", such as chlorophyll and hemoglobin, it has become a prime synthetic target for optoelectronic properties and in the design of metal complexes. During one such early expedition on the synthesis of porphyrin, Woodward proposed that condensing pyrrole with an aldehyde under acidic conditions yields the "precursor" porphyrinogen macrocycle. Its four-electron oxidation leads to the "transitory" 20π isophlorin, which undergoes subsequent two-electron oxidation to form the 18π "porphyrin". Due to its fleeting lifetime, it has been a synthetic challenge to stabilize the tetrapyrrolic isophlorin. This macrocycle symbolizes the antiaromatic character of a porphyrin-like macrocycle. In addition, the pyrrole NH also plays a key role in the proton-coupled, two-electron oxidation of isophlorin to the aromatic porphyrin. However, a major aspect of its unstable nature was attributed to its antiaromatic character, which is understood to destabilize the macrocycle upon conjugation. Antiaromaticity in general has not gained significant attention mainly due to the lack of stable 4nπ systems. In this regard, a stable isophlorin and its derivatives provide a glimmering hope to peek into the world of antiaromatic systems. This review will focus on the attempted synthesis of antiaromatic isophlorin ever since its conception. Based on recent synthetic advances, the chemistry of isophlorins can be expected to blossom into expanded derivatives of this antiaromatic macrocycle. Along with the synthetic details, the structural, electronic, and redox properties of isophlorin and its expanded derivatives will be elaborated.
